Sparse index: integrate with sparse-checkout

This series is based on ds/sparse-colon-path.

This series integrates the 'git sparse-checkout' builtin with the sparse index. This is the last integration that we fast-tracked into the microsoft/git fork. After this, we have no work in flight that would conflict with a Google Summer of Code project in this area.

The tricky part about the sparse-checkout builtin is that we actually do need to expand the index when growing the sparse-checkout boundary. The trick is to expand it only as far as we need it, and then ensure that we collapse any removed directories before the command completes.

To do this, we introduce a concept of a "partially expanded" index. In fact, we break the boolean sparse_index member into an enum with three states:

* COMPLETELY_FULL (0): No sparse directories exist.

* COMPLETELY_SPARSE (1): Sparse directories may exist. Files outside the sparse-checkout cone are reduced to sparse directory entries whenever possible.

* PARTIALLY_SPARSE (2): Sparse directories may exist. Some file entries outside the sparse-checkout cone may exist. Running convert_to_sparse() may further reduce those files to sparse directory entries.

Most of the patches in this series focus on introducing this enum and carefully converting previous uses of the boolean to use the enum. Some additional work is required to refactor ensure_full_index() into a new expand_to_pattern_list() method, as they are doing essentially the same thing, but with different scopes.

The result is improved performance on the sparse-checkout builtin as demonstrated in a new p2000-sparse-operations.sh performance test:

Test HEAD~1 HEAD
================

2000.24: git sparse-checkout ... (sparse-v3) 2.14(1.55+0.58) 1.57(1.03+0.53) -26.6% 2000.25: git sparse-checkout ... (sparse-v4) 2.20(1.62+0.57) 1.58(0.98+0.59) -28.2%

The improvement here is less dramatic because the operation is dominated by writing and deleting a lot of files in the worktree. A repeated no-op operation such as git sparse-checkout set $SPARSE_CONE would show a greater improvement, but is less interesting since it could gain that improvement without satisfying the "hard" parts of this builtin.

I specifically chose how to update the tests in t1092 and p2000 to avoid conflicts with Victoria's 'git stash' work.

Thanks, -Stolee

Derrick Stolee (8):
sparse-index: create expand_to_pattern_list()
sparse-index: introduce partially-sparse indexes
cache-tree: implement cache_tree_find_path()
sparse-checkout: --no-sparse-index needs a full index
sparse-index: partially expand directories
sparse-index: complete partial expansion
p2000: add test for 'git sparse-checkout [add|set]'
sparse-checkout: integrate with sparse index

 builtin/sparse-checkout.c                |   8 +-
 cache-tree.c                             |  24 +++++
 cache-tree.h                             |   2 +
 cache.h                                  |  32 ++++--
 read-cache.c                             |   6 +-
 sparse-index.c                           | 126 ++++++++++++++++++++---
 sparse-index.h                           |  14 +++
 t/perf/p2000-sparse-operations.sh        |   1 +
 t/t1092-sparse-checkout-compatibility.sh |  25 +++++
 unpack-trees.c                           |   4 +
 10 files changed, 214 insertions(+), 28 deletions(-)

base-commit: 124b05b23005437fa5fb91863bde2a8f5840e164
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1208%2Fderrickstolee%2Fsparse-index%2Fsparse-checkout-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1208/derrickstolee/sparse-index/sparse-checkout-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1208

gitgitgadget

From: Derrick Stolee <[email protected]>

This is the first change in a series to allow modifying the sparse-checkout pattern set without expanding a sparse index to a full one in the process. Here, we focus on the problem of expanding the pattern set through a command like 'git sparse-checkout add <path>' which needs to create new index entries for the paths now being written to the worktree.

To achieve this, we need to be able to replace sparse directory entries with their contained files and subdirectories. Once this is complete, other code paths can discover those cache entries and write the corresponding files to disk before committing the index.

We already have logic in ensure_full_index() that expands the index entries, so we will use that as our base. Create a new method, expand_to_pattern_list(), which takes a pattern list, but for now mostly ignores it. The current implementation is only correct when the pattern list is NULL as that does the same as ensure_full_index(). In fact, ensure_full_index() is converted to a shim over expand_to_pattern_list().

A future update will actually implement expand_to_pattern_list() to its full capabilities. For now, it is created and documented.

---
 sparse-index.c | 35 ++++++++++++++++++++++++++++++++---
 sparse-index.h | 14 ++++++++++++++
 2 files changed, 46 insertions(+), 3 deletions(-)

index 8636af72de5..37c7df877a6 100644
@@ -248,19 +248,41 @@ static int add_path_to_index(const struct object_id *oid,
 	return 0;
 }
 
-void ensure_full_index(struct index_state *istate)
+void expand_to_pattern_list(struct index_state *istate,
+			      struct pattern_list *pl)
 {
 	int i;
 	struct index_state *full;
 	struct strbuf base = STRBUF_INIT;
 
+	/*
+	 * If the index is already full, then keep it full. We will convert
+	 * it to a sparse index on write, if possible.
+	 */
 	if (!istate || !istate->sparse_index)
 		return;
 
+	/*
+	 * If our index is sparse, but our new pattern set does not use
+	 * cone mode patterns, then we need to expand the index before we
+	 * continue. A NULL pattern set indicates a full expansion to a
+	 * full index.
+	 */
+	if (pl && !pl->use_cone_patterns)
+		pl = NULL;
+
 	if (!istate->repo)
 		istate->repo = the_repository;
 
-	trace2_region_enter("index", "ensure_full_index", istate->repo);
+	/*
+	 * A NULL pattern set indicates we are expanding a full index, so
+	 * we use a special region name that indicates the full expansion.
+	 * This is used by test cases, but also helps to differentiate the
+	 * two cases.
+	 */
+	trace2_region_enter("index",
+			    pl ? "expand_to_pattern_list" : "ensure_full_index",
+			    istate->repo);
 
 	/* initialize basics of new index */
 	full = xcalloc(1, sizeof(struct index_state));

@@ -322,7 +344,14 @@ void ensure_full_index(struct index_state *istate)
 	cache_tree_free(&istate->cache_tree);
 	cache_tree_update(istate, 0);
 
-	trace2_region_leave("index", "ensure_full_index", istate->repo);
+	trace2_region_leave("index",
+			    pl ? "expand_to_pattern_list" : "ensure_full_index",
+			    istate->repo);
+}
+
+void ensure_full_index(struct index_state *istate)
+{
+	expand_to_pattern_list(istate, NULL);
 }
 
 void ensure_correct_sparsity(struct index_state *istate)

index 633d4fb7e31..037b541f49d 100644
@@ -23,4 +23,18 @@ void expand_to_path(struct index_state *istate,
 struct repository;
 int set_sparse_index_config(struct repository *repo, int enable);
 
+struct pattern_list;
+
+/**
+ * Scan the given index and compare its entries to the given pattern list.
+ * If the index is sparse and the pattern list uses cone mode patterns,
+ * then modify the index to contain the all of the file entries within that
+ * new pattern list. This expands sparse directories only as far as needed.
+ *
+ * If the pattern list is NULL or does not use cone mode patterns, then the
+ * index is expanded to a full index.
+ */
+void expand_to_pattern_list(struct index_state *istate,
+			      struct pattern_list *pl);
+
 #endif

gitgitgadget

You're right. When I saw this I thought it was just the "off by one" issue when patches have a "+" in the beginning, but it's actually the backwards order. Thanks for catching it.

-Stolee

From: Derrick Stolee <[email protected]>

A future change will present a temporary, in-memory mode where the index can both contain sparse directory entries but also not be completely collapsed to the smallest possible sparse directories. This will be necessary for modifying the sparse-checkout definition while using a sparse index.

For now, convert the single-bit member 'sparse_index' in 'struct index_state' to be a an 'enum sparse_index_mode' with three modes:

* COMPLETELY_FULL (0): No sparse directories exist.

* COMPLETELY_SPARSE (1): Sparse directories may exist. Files outside the sparse-checkout cone are reduced to sparse directory entries whenever possible.

* PARTIALLY_SPARSE (2): Sparse directories may exist. Some file entries outside the sparse-checkout cone may exist. Running convert_to_sparse() may further reduce those files to sparse directory entries.

The main reason to store this extra information is to allow convert_to_sparse() to short-circuit when the index is already in COMPLETELY_SPARSE mode but to actually do the necessary work when in PARTIALLY_SPARSE mode.

The PARTIALLY_SPARSE mode will be used in an upcoming change.

---
 builtin/sparse-checkout.c |  2 +-
 cache.h                   | 32 ++++++++++++++++++++++++--------
 read-cache.c              |  6 +++---
 sparse-index.c            |  6 +++---
 4 files changed, 31 insertions(+), 15 deletions(-)

index 0217d44c5b1..88eea069ad4 100644
@@ -128,7 +128,7 @@ static void clean_tracked_sparse_directories(struct repository *r)
 	 * sparse index will not delete directories that contain
 	 * conflicted entries or submodules.
 	 */
-	if (!r->index->sparse_index) {
+	if (r->index->sparse_index == COMPLETELY_FULL) {
 		/*
 		 * If something, such as a merge conflict or other concern,
 		 * prevents us from converting to a sparse index, then do

index 6226f6a8a53..2d067aca2fd 100644
@@ -310,6 +310,28 @@ struct untracked_cache;
 struct progress;
 struct pattern_list;
 
+enum sparse_index_mode {
+	/*
+	 * COMPLETELY_FULL: there are no sparse directories
+	 * in the index at all.
+	 */
+	COMPLETELY_FULL = 0,
+
+	/*
+	 * COLLAPSED: the index has already been collapsed to sparse
+	 * directories whereever possible.
+	 */
+	COLLAPSED = 1,
+
+	/*
+	 * PARTIALLY_SPARSE: the sparse directories that exist are
+	 * outside the sparse-checkout boundary, but it is possible
+	 * that some file entries could collapse to sparse directory
+	 * entries.
+	 */
+	PARTIALLY_SPARSE = 2,
+};
+
 struct index_state {
 	struct cache_entry **cache;
 	unsigned int version;

@@ -323,14 +345,8 @@ struct index_state {
 		 drop_cache_tree : 1,
 		 updated_workdir : 1,
 		 updated_skipworktree : 1,
-		 fsmonitor_has_run_once : 1,
-
-		 /*
-		  * sparse_index == 1 when sparse-directory
-		  * entries exist. Requires sparse-checkout
-		  * in cone mode.
-		  */
-		 sparse_index : 1;
+		 fsmonitor_has_run_once : 1;
+	enum sparse_index_mode sparse_index;
 	struct hashmap name_hash;
 	struct hashmap dir_hash;
 	struct object_id oid;

index 4df97e185e9..cb9b33169fd 100644
@@ -112,7 +112,7 @@ static const char *alternate_index_output;
 static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
 {
 	if (S_ISSPARSEDIR(ce->ce_mode))
-		istate->sparse_index = 1;
+		istate->sparse_index = COLLAPSED;
 
 	istate->cache[nr] = ce;
 	add_name_hash(istate, ce);

@@ -1856,7 +1856,7 @@ static int read_index_extension(struct index_state *istate,
 		break;
 	case CACHE_EXT_SPARSE_DIRECTORIES:
 		/* no content, only an indicator */
-		istate->sparse_index = 1;
+		istate->sparse_index = COLLAPSED;
 		break;
 	default:
 		if (*ext < 'A' || 'Z' < *ext)

@@ -3149,7 +3149,7 @@ static int do_write_locked_index(struct index_state *istate, struct lock_file *l
 				 unsigned flags)
 {
 	int ret;
-	int was_full = !istate->sparse_index;
+	int was_full = istate->sparse_index == COMPLETELY_FULL;
 
 	ret = convert_to_sparse(istate, 0);
 

index 37c7df877a6..79e8ff087bc 100644
@@ -173,7 +173,7 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	 * If the index is already sparse, empty, or otherwise
 	 * cannot be converted to sparse, do not convert.
 	 */
-	if (istate->sparse_index || !istate->cache_nr ||
+	if (istate->sparse_index == COLLAPSED || !istate->cache_nr ||
 	    !is_sparse_index_allowed(istate, flags))
 		return 0;
 

@@ -214,7 +214,7 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	FREE_AND_NULL(istate->fsmonitor_dirty);
 	FREE_AND_NULL(istate->fsmonitor_last_update);
 
-	istate->sparse_index = 1;
+	istate->sparse_index = COLLAPSED;
 	trace2_region_leave("index", "convert_to_sparse", istate->repo);
 	return 0;
 }

@@ -259,7 +259,7 @@ void expand_to_pattern_list(struct index_state *istate,
 	 * If the index is already full, then keep it full. We will convert
 	 * it to a sparse index on write, if possible.
 	 */
-	if (!istate || !istate->sparse_index)
+	if (!istate || istate->sparse_index == COMPLETELY_FULL)
 		return;
 
 	/*

gitgitgadget

From: Derrick Stolee <[email protected]>

Given a 'struct cache_tree', it may be beneficial to navigate directly to a node within that corresponds to a given path name. Create cache_tree_find_path() for this function. It returns NULL when no such path exists.

The implementation is adapted from do_invalidate_path() which does a similar search but also modifies the nodes it finds along the way.

This new method is not currently used, but will be in an upcoming change.

---
 cache-tree.c | 24 ++++++++++++++++++++++++
 cache-tree.h |  2 ++
 2 files changed, 26 insertions(+)

index 6752f69d515..23893a7b113 100644
@@ -100,6 +100,30 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
 	return find_subtree(it, path, pathlen, 1);
 }
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path)
+{
+	const char *slash;
+	int namelen;
+	struct cache_tree_sub *down;
+
+	if (!it)
+		return NULL;
+	slash = strchrnul(path, '/');
+	namelen = slash - path;
+	it->entry_count = -1;
+	if (!*slash) {
+		int pos;
+		pos = cache_tree_subtree_pos(it, path, namelen);
+		if (0 <= pos)
+			return it->down[pos]->cache_tree;
+		return NULL;
+	}
+	down = find_subtree(it, path, namelen, 0);
+	if (down)
+		return cache_tree_find_path(down->cache_tree, slash + 1);
+	return NULL;
+}
+
 static int do_invalidate_path(struct cache_tree *it, const char *path)
 {
 	/* a/b/c

index 8efeccebfc9..f75f8e74dcd 100644
@@ -29,6 +29,8 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *, const char *);
 
 int cache_tree_subtree_pos(struct cache_tree *it, const char *path, int pathlen);
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path);
+
 void cache_tree_write(struct strbuf *, struct cache_tree *root);
 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size);
 

gitgitgadget

From: Derrick Stolee <[email protected]>

When the --no-sparse-index option is supplied, the sparse-checkout builtin should explicitly ask to expand a sparse index to a full one. This is currently done implicitly due to the command_requires_full_index protection, but that will be removed in an upcoming change.

---
 builtin/sparse-checkout.c | 3 +++
 1 file changed, 3 insertions(+)

index 88eea069ad4..cbff6ad00b0 100644
@@ -413,6 +413,9 @@ static int update_modes(int *cone_mode, int *sparse_index)
 		/* force an index rewrite */
 		repo_read_index(the_repository);
 		the_repository->index->updated_workdir = 1;
+
+		if (!*sparse_index)
+			ensure_full_index(the_repository->index);
 	}
 
 	return 0;

gitgitgadget

From: Derrick Stolee <[email protected]>

The expand_to_pattern_list() method expands sparse directory entries to their list of contained files when either the pattern list is NULL or the directory is contained in the new pattern list's cone mode patterns.

It is possible that the pattern list has a recursive match with a directory 'A/B/C/' and so an existing sparse directory 'A/B/' would need to be expanded. If there exists a directory 'A/B/D/', then that directory should not be expanded and instead we can create a sparse directory.

To implement this, we plug into the add_path_to_index() callback for the call to read_tree_at(). Since we now need access to both the index we are writing and the pattern list we are comparing, create a 'struct modify_index_context' to use as a data transfer object. It is important that we use the given pattern list since we will use this pattern list to change the sparse-checkout patterns and cannot use istate->sparse_checkout_patterns.

---
 sparse-index.c | 46 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 7 deletions(-)

index 79e8ff087bc..3d8eed585b5 100644
@@ -9,6 +9,11 @@
 #include "dir.h"
 #include "fsmonitor.h"
 
+struct modify_index_context {
+	struct index_state *write;
+	struct pattern_list *pl;
+};
+
 static struct cache_entry *construct_sparse_dir_entry(
 				struct index_state *istate,
 				const char *sparse_dir,

@@ -231,18 +236,41 @@ static int add_path_to_index(const struct object_id *oid,
 			     struct strbuf *base, const char *path,
 			     unsigned int mode, void *context)
 {
-	struct index_state *istate = (struct index_state *)context;
+	struct modify_index_context *ctx = (struct modify_index_context *)context;
 	struct cache_entry *ce;
 	size_t len = base->len;
 
-	if (S_ISDIR(mode))
-		return READ_TREE_RECURSIVE;
+	if (S_ISDIR(mode)) {
+		int dtype;
+		size_t baselen = base->len;
+		if (!ctx->pl)
+			return READ_TREE_RECURSIVE;
 
-	strbuf_addstr(base, path);
+		/*
+		 * Have we expanded to a point outside of the sparse-checkout?
+		 */
+		strbuf_addstr(base, path);
+		strbuf_add(base, "/-", 2);
+
+		if (path_matches_pattern_list(base->buf, base->len,
+					      NULL, &dtype,
+					      ctx->pl, ctx->write)) {
+			strbuf_setlen(base, baselen);
+			return READ_TREE_RECURSIVE;
+		}
 
-	ce = make_cache_entry(istate, mode, oid, base->buf, 0, 0);
+		/*
+		 * The path "{base}{path}/" is a sparse directory. Create the correct
+		 * name for inserting the entry into the idnex.
+		 */
+		strbuf_setlen(base, base->len - 1);
+	} else {
+		strbuf_addstr(base, path);
+	}
+
+	ce = make_cache_entry(ctx->write, mode, oid, base->buf, 0, 0);
 	ce->ce_flags |= CE_SKIP_WORKTREE | CE_EXTENDED;
-	set_index_entry(istate, istate->cache_nr++, ce);
+	set_index_entry(ctx->write, ctx->write->cache_nr++, ce);
 
 	strbuf_setlen(base, len);
 	return 0;

@@ -254,6 +282,7 @@ void expand_to_pattern_list(struct index_state *istate,
 	int i;
 	struct index_state *full;
 	struct strbuf base = STRBUF_INIT;
+	struct modify_index_context ctx;
 
 	/*
 	 * If the index is already full, then keep it full. We will convert

@@ -294,6 +323,9 @@ void expand_to_pattern_list(struct index_state *istate,
 	full->cache_nr = 0;
 	ALLOC_ARRAY(full->cache, full->cache_alloc);
 
+	ctx.write = full;
+	ctx.pl = pl;
+
 	for (i = 0; i < istate->cache_nr; i++) {
 		struct cache_entry *ce = istate->cache[i];
 		struct tree *tree;

@@ -319,7 +351,7 @@ void expand_to_pattern_list(struct index_state *istate,
 		strbuf_add(&base, ce->name, strlen(ce->name));
 
 		read_tree_at(istate->repo, tree, &base, &ps,
-			     add_path_to_index, full);
+			     add_path_to_index, &ctx);
 
 		/* free directory entries. full entries are re-used */
 		discard_cache_entry(ce);

gitgitgadget

From: Derrick Stolee <[email protected]>

To complete the implementation of expand_to_pattern_list(), we need to detect when a sparse directory entry should remain sparse. This avoids a full expansion, so we now need to use the PARTIALLY_SPARSE mode to indicate this state.

There still are no callers to this method, but we will add one in the next change.

---
 sparse-index.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

index 3d8eed585b5..0bad5503304 100644
@@ -297,8 +297,24 @@ void expand_to_pattern_list(struct index_state *istate,
 	 * continue. A NULL pattern set indicates a full expansion to a
 	 * full index.
 	 */
-	if (pl && !pl->use_cone_patterns)
+	if (pl && !pl->use_cone_patterns) {
 		pl = NULL;
+	} else {
+		/*
+		 * We might contract file entries into sparse-directory
+		 * entries, and for that we will need the cache tree to
+		 * be recomputed.
+		 */
+		cache_tree_free(&istate->cache_tree);
+
+		/*
+		 * If there is a problem creating the cache tree, then we
+		 * need to expand to a full index since we cannot satisfy
+		 * the current request as a sparse index.
+		 */
+		if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
+			pl = NULL;
+	}
 
 	if (!istate->repo)
 		istate->repo = the_repository;

@@ -317,8 +333,14 @@ void expand_to_pattern_list(struct index_state *istate,
 	full = xcalloc(1, sizeof(struct index_state));
 	memcpy(full, istate, sizeof(struct index_state));
 
+	/*
+	 * This slightly-misnamed 'full' index might still be sparse if we
+	 * are only modifying the list of sparse directories. This hinges
+	 * on whether we have a non-NULL pattern list.
+	 */
+	full->sparse_index = pl ? PARTIALLY_SPARSE : COMPLETELY_FULL;
+
 	/* then change the necessary things */
-	full->sparse_index = 0;
 	full->cache_alloc = (3 * istate->cache_alloc) / 2;
 	full->cache_nr = 0;
 	ALLOC_ARRAY(full->cache, full->cache_alloc);

@@ -330,11 +352,22 @@ void expand_to_pattern_list(struct index_state *istate,
 		struct cache_entry *ce = istate->cache[i];
 		struct tree *tree;
 		struct pathspec ps;
+		int dtype;
 
 		if (!S_ISSPARSEDIR(ce->ce_mode)) {
 			set_index_entry(full, full->cache_nr++, ce);
 			continue;
 		}
+
+		/* We now have a sparse directory entry. Should we expand? */
+		if (pl &&
+		    path_matches_pattern_list(ce->name, ce->ce_namelen,
+					      NULL, &dtype,
+					      pl, istate) <= 0) {
+			set_index_entry(full, full->cache_nr++, ce);
+			continue;
+		}
+
 		if (!(ce->ce_flags & CE_SKIP_WORKTREE))
 			warning(_("index entry is a directory, but not sparse (%08x)"),
 				ce->ce_flags);

@@ -360,7 +393,7 @@ void expand_to_pattern_list(struct index_state *istate,
 	/* Copy back into original index. */
 	memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
 	memcpy(&istate->dir_hash, &full->dir_hash, sizeof(full->dir_hash));
-	istate->sparse_index = 0;
+	istate->sparse_index = pl ? PARTIALLY_SPARSE : COMPLETELY_FULL;
 	free(istate->cache);
 	istate->cache = full->cache;
 	istate->cache_nr = full->cache_nr;

@@ -374,7 +407,7 @@ void expand_to_pattern_list(struct index_state *istate,
 
 	/* Clear and recompute the cache-tree */
 	cache_tree_free(&istate->cache_tree);
-	cache_tree_update(istate, 0);
+	cache_tree_update(istate, WRITE_TREE_MISSING_OK);
 
 	trace2_region_leave("index",
 			    pl ? "expand_to_pattern_list" : "ensure_full_index",

gitgitgadget

You are 100% correct, and using "== NOT_MATCHED" makes the intention clear, as well as being more robust to a breakage in path_matches_pattern_list().

Thanks,
-Stolee

From: Derrick Stolee <[email protected]>

The sparse-checkout builtin is almost completely integrated with the sparse index, allowing the sparse-checkout boundary to be modified without expanding a sparse index to a full one. Add a test to p2000-sparse-operations.sh that adds a directory to the sparse-checkout definition, then removes it. Using both operations is important to ensure that the operation is doing the same work in each repetition as well as leaving the test repo in a good state for later tests.

---
 t/perf/p2000-sparse-operations.sh | 1 +
 1 file changed, 1 insertion(+)

index 382716cfca9..ce5cfac5714 100755
@@ -110,6 +110,7 @@ test_perf_on_all git add -A
 test_perf_on_all git add .
 test_perf_on_all git commit -a -m A
 test_perf_on_all git checkout -f -
+test_perf_on_all "git sparse-checkout add f2/f3/f1 && git sparse-checkout set $SPARSE_CONE"
 test_perf_on_all git reset
 test_perf_on_all git reset --hard
 test_perf_on_all git reset -- does-not-exist

gitgitgadget

From: Derrick Stolee <[email protected]>

When modifying the sparse-checkout definition, the sparse-checkout builtin calls update_sparsity() to modify the SKIP_WORKTREE bits of all cache entries in the index. Before, we needed the index to be fully expanded in order to ensure we had the full list of files necessary that match the new patterns.

Insert a call to reset_sparse_directories() that expands sparse directories that are within the new pattern list, but only far enough that every necessary file path now exists as a cache entry. The remaining logic within update_sparsity() will modify the SKIP_WORKTREE bits appropriately.

This allows us to disable command_requires_full_index within the sparse-checkout builtin. Add tests that demonstrate that we are not expanding to a full index unnecessarily.

We can see the improved performance in the p2000 test script:

Test HEAD~1 HEAD
------------------------------------------------------------------------

2000.24: git ... (sparse-v3)   2.14(1.55+0.58)   1.57(1.03+0.53) -26.6%
2000.25: git ... (sparse-v4)   2.20(1.62+0.57)   1.58(0.98+0.59) -28.2%

These reductions of 26-28% are small compared to most examples, but the time is dominated by writing a new copy of the base repository to the worktree and then deleting it again. The fact that the previous index expansion was such a large portion of the time is telling how important it is to complete this sparse index integration.

---
 builtin/sparse-checkout.c                |  3 +++
 t/t1092-sparse-checkout-compatibility.sh | 25 ++++++++++++++++++++++++
 unpack-trees.c                           |  4 ++++
 3 files changed, 32 insertions(+)

index cbff6ad00b0..0157b292b36 100644
@@ -937,6 +937,9 @@ int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config, NULL);
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	if (argc > 0) {
 		if (!strcmp(argv[0], "list"))
 			return sparse_checkout_list(argc, argv);

index 93bcfd20bbc..614357fc48c 100755
@@ -1552,6 +1552,31 @@ test_expect_success 'ls-files' '
 	ensure_not_expanded ls-files --sparse
 '
 
+test_expect_success 'sparse index is not expanded: sparse-checkout' '
+	init_repos &&
+
+	ensure_not_expanded sparse-checkout set deep/deeper2 &&
+	ensure_not_expanded sparse-checkout set deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set deep &&
+	ensure_not_expanded sparse-checkout add folder1 &&
+	ensure_not_expanded sparse-checkout set deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set folder2 &&
+
+	# Demonstrate that the checks that "folder1/a" is a file
+	# do not cause a sparse-index expansion (since it is in the
+	# sparse-checkout cone).
+	echo >>sparse-index/folder2/a &&
+	git -C sparse-index add folder2/a &&
+
+	ensure_not_expanded sparse-checkout add folder1 &&
+
+	# Skip checks here, since deep/deeper1 is inside a sparse directory
+	# that must be expanded to check whether `deep/deeper1` is a file
+	# or not.
+	ensure_not_expanded sparse-checkout set --skip-checks deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set
+'
+
 # NEEDSWORK: a sparse-checkout behaves differently from a full checkout
 # in this scenario, but it shouldn't.
 test_expect_success 'reset mixed and checkout orphan' '

index 7f528d35cc2..9745e0dfc34 100644
@@ -18,6 +18,7 @@
 #include "promisor-remote.h"
 #include "entry.h"
 #include "parallel-checkout.h"
+#include "sparse-index.h"
 
 /*
  * Error messages expected by scripts out of plumbing commands such as

@@ -2018,6 +2019,9 @@ enum update_sparsity_result update_sparsity(struct unpack_trees_options *o)
 			goto skip_sparse_checkout;
 	}
 
+	/* Expand sparse directories as needed */
+	expand_to_pattern_list(o->src_index, o->pl);
+
 	/* Set NEW_SKIP_WORKTREE on existing entries. */
 	mark_all_ce_unused(o->src_index);
 	mark_new_skip_worktree(o->pl, o->src_index, 0,

gitgitgadget

I guess I was relying on tests added previously for the sparse index, such as this one:

test_expect_success 'sparse-index contents' '

	init_repos &&

	git -C sparse-index ls-files --sparse --stage >cache &&
	for dir in folder1 folder2 x
	do
		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
		grep "040000 $TREE 0	$dir/" cache \
			|| return 1
	done &&

	git -C sparse-index sparse-checkout set folder1 &&

	git -C sparse-index ls-files --sparse --stage >cache &&
	for dir in deep folder2 x
	do
		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
		grep "040000 $TREE 0	$dir/" cache \
			|| return 1
	done &&

	git -C sparse-index sparse-checkout set deep/deeper1 &&

	git -C sparse-index ls-files --sparse --stage >cache &&
	for dir in deep/deeper2 folder1 folder2 x
	do
		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
		grep "040000 $TREE 0	$dir/" cache \
			|| return 1
	done &&

	# Disabling the sparse-index replaces tree entries with full ones
	git -C sparse-index sparse-checkout init --no-sparse-index &&
	test_sparse_match git ls-files --stage --sparse

'

But this test isn't covering enough interesting cases that might cause issues with the changes in this series. I'll add a patch that increases coverage in this area.

Thanks,
-Stolee

This series is based on ds/sparse-colon-path.

This series integrates the 'git sparse-checkout' builtin with the sparse index. This is the last integration that we fast-tracked into the microsoft/git fork. After this, we have no work in flight that would conflict with a Google Summer of Code project in this area.

The tricky part about the sparse-checkout builtin is that we actually do need to expand the index when growing the sparse-checkout boundary. The trick is to expand it only as far as we need it, and then ensure that we collapse any removed directories before the command completes.

To do this, we introduce a concept of a "partially expanded" index. In fact, we break the boolean sparse_index member into an enum with three states:

* COMPLETELY_FULL (0): No sparse directories exist.

* COMPLETELY_SPARSE (1): Sparse directories may exist. Files outside the sparse-checkout cone are reduced to sparse directory entries whenever possible.

* PARTIALLY_SPARSE (2): Sparse directories may exist. Some file entries outside the sparse-checkout cone may exist. Running convert_to_sparse() may further reduce those files to sparse directory entries.

Most of the patches in this series focus on introducing this enum and carefully converting previous uses of the boolean to use the enum. Some additional work is required to refactor ensure_full_index() into a new expand_to_pattern_list() method, as they are doing essentially the same thing, but with different scopes.

The result is improved performance on the sparse-checkout builtin as demonstrated in a new p2000-sparse-operations.sh performance test:

Test HEAD~1 HEAD
================

2000.24: git sparse-checkout ... (sparse-v3) 2.14(1.55+0.58) 1.57(1.03+0.53) -26.6% 2000.25: git sparse-checkout ... (sparse-v4) 2.20(1.62+0.57) 1.58(0.98+0.59) -28.2%

The improvement here is less dramatic because the operation is dominated by writing and deleting a lot of files in the worktree. A repeated no-op operation such as git sparse-checkout set $SPARSE_CONE would show a greater improvement, but is less interesting since it could gain that improvement without satisfying the "hard" parts of this builtin.

I specifically chose how to update the tests in t1092 and p2000 to avoid conflicts with Victoria's 'git stash' work.

Updates in v2
=============

* Typo fixes.
* Two patches are added to the start to (a) refactor existing sparse index content tests, and (b) add new sparse index content tests with additional scenarios.
* Use NOT_MATCHED directly instead of implicitly allowing UNDECIDED when matching in cone mode.

Thanks, -Stolee

Derrick Stolee (10):
t1092: refactor 'sparse-index contents' test
t1092: stress test 'git sparse-checkout set'
sparse-index: create expand_to_pattern_list()
sparse-index: introduce partially-sparse indexes
cache-tree: implement cache_tree_find_path()
sparse-checkout: --no-sparse-index needs a full index
sparse-index: partially expand directories
sparse-index: complete partial expansion
p2000: add test for 'git sparse-checkout [add|set]'
sparse-checkout: integrate with sparse index

 builtin/sparse-checkout.c                |   8 +-
 cache-tree.c                             |  24 +++++
 cache-tree.h                             |   2 +
 cache.h                                  |  32 ++++--
 read-cache.c                             |   6 +-
 sparse-index.c                           | 126 ++++++++++++++++++++---
 sparse-index.h                           |  14 +++
 t/perf/p2000-sparse-operations.sh        |   1 +
 t/t1092-sparse-checkout-compatibility.sh |  95 +++++++++++++----
 unpack-trees.c                           |   4 +
 10 files changed, 265 insertions(+), 47 deletions(-)

base-commit: 124b05b23005437fa5fb91863bde2a8f5840e164
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1208%2Fderrickstolee%2Fsparse-index%2Fsparse-checkout-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1208/derrickstolee/sparse-index/sparse-checkout-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1208

Range-diff vs v1:

  -:  ----------- >  1:  f2960747ed8 t1092: refactor 'sparse-index contents' test
  -:  ----------- >  2:  5030eeecf4f t1092: stress test 'git sparse-checkout set'
  1:  f1194d56d33 !  3:  d15338573e5 sparse-index: create expand_to_pattern_list()

@@ sparse-index.c: static int add_path_to_index(const struct object_id *oid,

-void ensure_full_index(struct index_state *istate) +void expand_to_pattern_list(struct index_state *istate,
-+ struct pattern_list *pl)
++ struct pattern_list *pl)
{
int i;
struct index_state *full;

  2:  d394d0e20e8 =  4:  269c206c331 sparse-index: introduce partially-sparse indexes
  3:  c0e81be97aa =  5:  c977001c033 cache-tree: implement cache_tree_find_path()
  4:  d1fb2e0e0d3 =  6:  e42463de0d2 sparse-checkout: --no-sparse-index needs a full index
  5:  5c7546ab070 !  7:  346c56bf256 sparse-index: partially expand directories
     @@ sparse-index.c: static int add_path_to_index(const struct object_id *oid,
      -	ce = make_cache_entry(istate, mode, oid, base->buf, 0, 0);
      +		/*
      +		 * The path "{base}{path}/" is a sparse directory. Create the correct
     -+		 * name for inserting the entry into the idnex.
     ++		 * name for inserting the entry into the index.
      +		 */
      +		strbuf_setlen(base, base->len - 1);
      +	} else {
  6:  eba63cc12af !  8:  ed640e3645b sparse-index: complete partial expansion
     @@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
      +		if (pl &&
      +		    path_matches_pattern_list(ce->name, ce->ce_namelen,
      +					      NULL, &dtype,
     -+					      pl, istate) <= 0) {
     ++					      pl, istate) == NOT_MATCHED) {
      +			set_index_entry(full, full->cache_nr++, ce);
      +			continue;
      +		}
  7:  2804326c8bb =  9:  089ab086f58 p2000: add test for 'git sparse-checkout [add|set]'
  8:  b8a349c6dee = 10:  ad9ed6973d5 sparse-checkout: integrate with sparse index

gitgitgadget

From: Derrick Stolee <[email protected]>

Before expanding this test with more involved cases, first extract the repeated logic into a new test_sparse_checkout_set helper. This helper checks that 'git sparse-checkout set ...' succeeds and then verifies that certain directories have sparse directory entries in the sparse index. It also verifies that the in-cone directories are _not_ sparse directory entries in the sparse index.

---
 t/t1092-sparse-checkout-compatibility.sh | 53 ++++++++++++++++--------
 1 file changed, 35 insertions(+), 18 deletions(-)

index 93bcfd20bbc..e7c0ae9b953 100755
@@ -205,36 +205,53 @@ test_sparse_unstaged () {
 	done
 }
 
-test_expect_success 'sparse-index contents' '
-	init_repos &&
-
+# Usage: test_sprase_checkout_set "<c1> ... <cN>" "<s1> ... <sM>"
+# Verifies that "git sparse-checkout set <c1> ... <cN>" succeeds and
+# leaves the sparse index in a state where <s1> ... <sM> are sparse
+# directories (and <c1> ... <cN> are not).
+test_sparse_checkout_set () {
+	CONE_DIRS=$1 &&
+	SPARSE_DIRS=$2 &&
+	git -C sparse-index sparse-checkout set $CONE_DIRS &&
 	git -C sparse-index ls-files --sparse --stage >cache &&
-	for dir in folder1 folder2 x
+
+	# Check that the directories outside of the sparse-checkout cone
+	# have sparse directory entries.
+	for dir in $SPARSE_DIRS
 	do
 		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
 		grep "040000 $TREE 0	$dir/" cache \
 			|| return 1
 	done &&
 
-	git -C sparse-index sparse-checkout set folder1 &&
-
-	git -C sparse-index ls-files --sparse --stage >cache &&
-	for dir in deep folder2 x
+	# Check that the directories in the sparse-checkout cone
+	# are not sparse directory entries.
+	for dir in $CONE_DIRS
 	do
 		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
-		grep "040000 $TREE 0	$dir/" cache \
+		! grep "040000 $TREE 0	$dir/" cache \
 			|| return 1
-	done &&
+	done
+}
 
-	git -C sparse-index sparse-checkout set deep/deeper1 &&
+test_expect_success 'sparse-index contents' '
+	init_repos &&
 
-	git -C sparse-index ls-files --sparse --stage >cache &&
-	for dir in deep/deeper2 folder1 folder2 x
-	do
-		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
-		grep "040000 $TREE 0	$dir/" cache \
-			|| return 1
-	done &&
+	# Remove deep, add three other directories.
+	test_sparse_checkout_set \
+		"folder1 folder2 x" \
+		"before deep" &&
+
+	# Remove folder1, add deep
+	test_sparse_checkout_set \
+		"deep folder2 x" \
+		"before folder1" &&
+
+	# Replace deep with deep/deeper2 (dropping deep/deeper1)
+	# Add folder1
+	test_sparse_checkout_set \
+		"deep/deeper2 folder1 folder2 x" \
+		"before deep/deeper1" &&
 
 	# Disabling the sparse-index replaces tree entries with full ones
 	git -C sparse-index sparse-checkout init --no-sparse-index &&

gitgitgadget

From: Derrick Stolee <[email protected]>

The 'sparse-index contents' test checks that the sparse index has the correct set of sparse directories in the index after modifying the cone mode patterns using 'git sparse-checkout set'. Add to the coverage here by adding more complicated scenarios that were not previously tested.

In order to check paths that do not exist at HEAD, we need to modify the test_sparse_checkout_set helper slightly:

1. Add the --skip-checks argument to the 'set' command to avoid failures when passing paths that do not exist at HEAD.

2. When looking for the non-existence of sparse directories for the paths in $CONE_DIRS, allow the rev-list command to fail because the path does not exist at HEAD.

This allows us to add some interesting test cases.

---
 t/t1092-sparse-checkout-compatibility.sh | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

index e7c0ae9b953..785820f9fd5 100755
@@ -212,7 +212,7 @@ test_sparse_unstaged () {
 test_sparse_checkout_set () {
 	CONE_DIRS=$1 &&
 	SPARSE_DIRS=$2 &&
-	git -C sparse-index sparse-checkout set $CONE_DIRS &&
+	git -C sparse-index sparse-checkout set --skip-checks $CONE_DIRS &&
 	git -C sparse-index ls-files --sparse --stage >cache &&
 
 	# Check that the directories outside of the sparse-checkout cone

@@ -228,7 +228,9 @@ test_sparse_checkout_set () {
 	# are not sparse directory entries.
 	for dir in $CONE_DIRS
 	do
-		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
+		# Allow TREE to not exist because
+		# $dir does not exist at HEAD.
+		TREE=$(git -C sparse-index rev-parse HEAD:$dir) ||
 		! grep "040000 $TREE 0	$dir/" cache \
 			|| return 1
 	done

@@ -253,6 +255,19 @@ test_expect_success 'sparse-index contents' '
 		"deep/deeper2 folder1 folder2 x" \
 		"before deep/deeper1" &&
 
+	# Replace deep/deeper2 with deep/deeper1
+	# Replace folder1 with folder1/0/0
+	# Replace folder2 with non-existent folder2/2/3
+	# Add non-existent "bogus"
+	test_sparse_checkout_set \
+		"bogus deep/deeper1 folder1/0/0 folder2/2/3 x" \
+		"before deep/deeper2 folder2/0" &&
+
+	# Drop down to only files at root
+	test_sparse_checkout_set \
+		"" \
+		"before deep folder1 folder2 x" &&
+
 	# Disabling the sparse-index replaces tree entries with full ones
 	git -C sparse-index sparse-checkout init --no-sparse-index &&
 	test_sparse_match git ls-files --stage --sparse

gitgitgadget

From: Derrick Stolee <[email protected]>

This is the first change in a series to allow modifying the sparse-checkout pattern set without expanding a sparse index to a full one in the process. Here, we focus on the problem of expanding the pattern set through a command like 'git sparse-checkout add <path>' which needs to create new index entries for the paths now being written to the worktree.

To achieve this, we need to be able to replace sparse directory entries with their contained files and subdirectories. Once this is complete, other code paths can discover those cache entries and write the corresponding files to disk before committing the index.

We already have logic in ensure_full_index() that expands the index entries, so we will use that as our base. Create a new method, expand_to_pattern_list(), which takes a pattern list, but for now mostly ignores it. The current implementation is only correct when the pattern list is NULL as that does the same as ensure_full_index(). In fact, ensure_full_index() is converted to a shim over expand_to_pattern_list().

A future update will actually implement expand_to_pattern_list() to its full capabilities. For now, it is created and documented.

---
 sparse-index.c | 35 ++++++++++++++++++++++++++++++++---
 sparse-index.h | 14 ++++++++++++++
 2 files changed, 46 insertions(+), 3 deletions(-)

index 8636af72de5..2a06ef58051 100644
@@ -248,19 +248,41 @@ static int add_path_to_index(const struct object_id *oid,
 	return 0;
 }
 
-void ensure_full_index(struct index_state *istate)
+void expand_to_pattern_list(struct index_state *istate,
+			    struct pattern_list *pl)
 {
 	int i;
 	struct index_state *full;
 	struct strbuf base = STRBUF_INIT;
 
+	/*
+	 * If the index is already full, then keep it full. We will convert
+	 * it to a sparse index on write, if possible.
+	 */
 	if (!istate || !istate->sparse_index)
 		return;
 
+	/*
+	 * If our index is sparse, but our new pattern set does not use
+	 * cone mode patterns, then we need to expand the index before we
+	 * continue. A NULL pattern set indicates a full expansion to a
+	 * full index.
+	 */
+	if (pl && !pl->use_cone_patterns)
+		pl = NULL;
+
 	if (!istate->repo)
 		istate->repo = the_repository;
 
-	trace2_region_enter("index", "ensure_full_index", istate->repo);
+	/*
+	 * A NULL pattern set indicates we are expanding a full index, so
+	 * we use a special region name that indicates the full expansion.
+	 * This is used by test cases, but also helps to differentiate the
+	 * two cases.
+	 */
+	trace2_region_enter("index",
+			    pl ? "expand_to_pattern_list" : "ensure_full_index",
+			    istate->repo);
 
 	/* initialize basics of new index */
 	full = xcalloc(1, sizeof(struct index_state));

@@ -322,7 +344,14 @@ void ensure_full_index(struct index_state *istate)
 	cache_tree_free(&istate->cache_tree);
 	cache_tree_update(istate, 0);
 
-	trace2_region_leave("index", "ensure_full_index", istate->repo);
+	trace2_region_leave("index",
+			    pl ? "expand_to_pattern_list" : "ensure_full_index",
+			    istate->repo);
+}
+
+void ensure_full_index(struct index_state *istate)
+{
+	expand_to_pattern_list(istate, NULL);
 }
 
 void ensure_correct_sparsity(struct index_state *istate)

index 633d4fb7e31..037b541f49d 100644
@@ -23,4 +23,18 @@ void expand_to_path(struct index_state *istate,
 struct repository;
 int set_sparse_index_config(struct repository *repo, int enable);
 
+struct pattern_list;
+
+/**
+ * Scan the given index and compare its entries to the given pattern list.
+ * If the index is sparse and the pattern list uses cone mode patterns,
+ * then modify the index to contain the all of the file entries within that
+ * new pattern list. This expands sparse directories only as far as needed.
+ *
+ * If the pattern list is NULL or does not use cone mode patterns, then the
+ * index is expanded to a full index.
+ */
+void expand_to_pattern_list(struct index_state *istate,
+			      struct pattern_list *pl);
+
 #endif

gitgitgadget

Sounds like a natural evolution of the API that used to be all-or-none to expand-only-those-that-match.

The old one had a sensible name to tell us that it is about the in-core index (and "full index" implied it was about sparse-index feature because what state other than "full" the index can be---some are shrunk into tree entries, which by definition is the sparse-index feature). Contrasted to that, the name of the new one is horrible. It does not even have index anywhere in the name.

I wonder expand_index() would work?

Makes sense. Good suggestion.

Good idea.

Thanks,
-Stolee

From: Derrick Stolee <[email protected]>

A future change will present a temporary, in-memory mode where the index can both contain sparse directory entries but also not be completely collapsed to the smallest possible sparse directories. This will be necessary for modifying the sparse-checkout definition while using a sparse index.

For now, convert the single-bit member 'sparse_index' in 'struct index_state' to be a an 'enum sparse_index_mode' with three modes:

* COMPLETELY_FULL (0): No sparse directories exist.

* COMPLETELY_SPARSE (1): Sparse directories may exist. Files outside the sparse-checkout cone are reduced to sparse directory entries whenever possible.

* PARTIALLY_SPARSE (2): Sparse directories may exist. Some file entries outside the sparse-checkout cone may exist. Running convert_to_sparse() may further reduce those files to sparse directory entries.

The main reason to store this extra information is to allow convert_to_sparse() to short-circuit when the index is already in COMPLETELY_SPARSE mode but to actually do the necessary work when in PARTIALLY_SPARSE mode.

The PARTIALLY_SPARSE mode will be used in an upcoming change.

---
 builtin/sparse-checkout.c |  2 +-
 cache.h                   | 32 ++++++++++++++++++++++++--------
 read-cache.c              |  6 +++---
 sparse-index.c            |  6 +++---
 4 files changed, 31 insertions(+), 15 deletions(-)

index 0217d44c5b1..88eea069ad4 100644
@@ -128,7 +128,7 @@ static void clean_tracked_sparse_directories(struct repository *r)
 	 * sparse index will not delete directories that contain
 	 * conflicted entries or submodules.
 	 */
-	if (!r->index->sparse_index) {
+	if (r->index->sparse_index == COMPLETELY_FULL) {
 		/*
 		 * If something, such as a merge conflict or other concern,
 		 * prevents us from converting to a sparse index, then do

index 6226f6a8a53..2d067aca2fd 100644
@@ -310,6 +310,28 @@ struct untracked_cache;
 struct progress;
 struct pattern_list;
 
+enum sparse_index_mode {
+	/*
+	 * COMPLETELY_FULL: there are no sparse directories
+	 * in the index at all.
+	 */
+	COMPLETELY_FULL = 0,
+
+	/*
+	 * COLLAPSED: the index has already been collapsed to sparse
+	 * directories whereever possible.
+	 */
+	COLLAPSED = 1,
+
+	/*
+	 * PARTIALLY_SPARSE: the sparse directories that exist are
+	 * outside the sparse-checkout boundary, but it is possible
+	 * that some file entries could collapse to sparse directory
+	 * entries.
+	 */
+	PARTIALLY_SPARSE = 2,
+};
+
 struct index_state {
 	struct cache_entry **cache;
 	unsigned int version;

@@ -323,14 +345,8 @@ struct index_state {
 		 drop_cache_tree : 1,
 		 updated_workdir : 1,
 		 updated_skipworktree : 1,
-		 fsmonitor_has_run_once : 1,
-
-		 /*
-		  * sparse_index == 1 when sparse-directory
-		  * entries exist. Requires sparse-checkout
-		  * in cone mode.
-		  */
-		 sparse_index : 1;
+		 fsmonitor_has_run_once : 1;
+	enum sparse_index_mode sparse_index;
 	struct hashmap name_hash;
 	struct hashmap dir_hash;
 	struct object_id oid;

index 4df97e185e9..cb9b33169fd 100644
@@ -112,7 +112,7 @@ static const char *alternate_index_output;
 static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
 {
 	if (S_ISSPARSEDIR(ce->ce_mode))
-		istate->sparse_index = 1;
+		istate->sparse_index = COLLAPSED;
 
 	istate->cache[nr] = ce;
 	add_name_hash(istate, ce);

@@ -1856,7 +1856,7 @@ static int read_index_extension(struct index_state *istate,
 		break;
 	case CACHE_EXT_SPARSE_DIRECTORIES:
 		/* no content, only an indicator */
-		istate->sparse_index = 1;
+		istate->sparse_index = COLLAPSED;
 		break;
 	default:
 		if (*ext < 'A' || 'Z' < *ext)

@@ -3149,7 +3149,7 @@ static int do_write_locked_index(struct index_state *istate, struct lock_file *l
 				 unsigned flags)
 {
 	int ret;
-	int was_full = !istate->sparse_index;
+	int was_full = istate->sparse_index == COMPLETELY_FULL;
 
 	ret = convert_to_sparse(istate, 0);
 

index 2a06ef58051..c2cd3bdb614 100644
@@ -173,7 +173,7 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	 * If the index is already sparse, empty, or otherwise
 	 * cannot be converted to sparse, do not convert.
 	 */
-	if (istate->sparse_index || !istate->cache_nr ||
+	if (istate->sparse_index == COLLAPSED || !istate->cache_nr ||
 	    !is_sparse_index_allowed(istate, flags))
 		return 0;
 

@@ -214,7 +214,7 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	FREE_AND_NULL(istate->fsmonitor_dirty);
 	FREE_AND_NULL(istate->fsmonitor_last_update);
 
-	istate->sparse_index = 1;
+	istate->sparse_index = COLLAPSED;
 	trace2_region_leave("index", "convert_to_sparse", istate->repo);
 	return 0;
 }

@@ -259,7 +259,7 @@ void expand_to_pattern_list(struct index_state *istate,
 	 * If the index is already full, then keep it full. We will convert
 	 * it to a sparse index on write, if possible.
 	 */
-	if (!istate || !istate->sparse_index)
+	if (!istate || istate->sparse_index == COMPLETELY_FULL)
 		return;
 
 	/*

gitgitgadget

The = 0 case matters because that is the default when the index struct is initialized to zero. The other values are not important.

Can do.

Would prepending with "INDEX_" be sufficient?

I can add that comment for the COMPLETELY_FULL enum value.

Thanks,
-Stolee

Yeah, index-collapsed, index-expanded, etc., sounds distinctive enough. Sorry, but I cannot think of a good phrase for partially expanded case that is short, succinct and would go well with the fully expanded and fully collapsed cases.

Thanks.

From: Derrick Stolee <[email protected]>

Given a 'struct cache_tree', it may be beneficial to navigate directly to a node within that corresponds to a given path name. Create cache_tree_find_path() for this function. It returns NULL when no such path exists.

The implementation is adapted from do_invalidate_path() which does a similar search but also modifies the nodes it finds along the way.

This new method is not currently used, but will be in an upcoming change.

---
 cache-tree.c | 24 ++++++++++++++++++++++++
 cache-tree.h |  2 ++
 2 files changed, 26 insertions(+)

index 6752f69d515..23893a7b113 100644
@@ -100,6 +100,30 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
 	return find_subtree(it, path, pathlen, 1);
 }
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path)
+{
+	const char *slash;
+	int namelen;
+	struct cache_tree_sub *down;
+
+	if (!it)
+		return NULL;
+	slash = strchrnul(path, '/');
+	namelen = slash - path;
+	it->entry_count = -1;
+	if (!*slash) {
+		int pos;
+		pos = cache_tree_subtree_pos(it, path, namelen);
+		if (0 <= pos)
+			return it->down[pos]->cache_tree;
+		return NULL;
+	}
+	down = find_subtree(it, path, namelen, 0);
+	if (down)
+		return cache_tree_find_path(down->cache_tree, slash + 1);
+	return NULL;
+}
+
 static int do_invalidate_path(struct cache_tree *it, const char *path)
 {
 	/* a/b/c

index 8efeccebfc9..f75f8e74dcd 100644
@@ -29,6 +29,8 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *, const char *);
 
 int cache_tree_subtree_pos(struct cache_tree *it, const char *path, int pathlen);
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path);
+
 void cache_tree_write(struct strbuf *, struct cache_tree *root);
 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size);
 

gitgitgadget

Good idea!

I think the abstraction definitely fit the shape of its consumers pretty perfectly. I wonder if having a method like this will make us think of new ways to use the cache tree for other things.

Thanks,
-Stolee

From: Derrick Stolee <[email protected]>

When the --no-sparse-index option is supplied, the sparse-checkout builtin should explicitly ask to expand a sparse index to a full one. This is currently done implicitly due to the command_requires_full_index protection, but that will be removed in an upcoming change.

---
 builtin/sparse-checkout.c | 3 +++
 1 file changed, 3 insertions(+)

index 88eea069ad4..cbff6ad00b0 100644
@@ -413,6 +413,9 @@ static int update_modes(int *cone_mode, int *sparse_index)
 		/* force an index rewrite */
 		repo_read_index(the_repository);
 		the_repository->index->updated_workdir = 1;
+
+		if (!*sparse_index)
+			ensure_full_index(the_repository->index);
 	}
 
 	return 0;

gitgitgadget

From: Derrick Stolee <[email protected]>

The expand_to_pattern_list() method expands sparse directory entries to their list of contained files when either the pattern list is NULL or the directory is contained in the new pattern list's cone mode patterns.

It is possible that the pattern list has a recursive match with a directory 'A/B/C/' and so an existing sparse directory 'A/B/' would need to be expanded. If there exists a directory 'A/B/D/', then that directory should not be expanded and instead we can create a sparse directory.

To implement this, we plug into the add_path_to_index() callback for the call to read_tree_at(). Since we now need access to both the index we are writing and the pattern list we are comparing, create a 'struct modify_index_context' to use as a data transfer object. It is important that we use the given pattern list since we will use this pattern list to change the sparse-checkout patterns and cannot use istate->sparse_checkout_patterns.

---
 sparse-index.c | 46 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 7 deletions(-)

index c2cd3bdb614..73b82e5017b 100644
@@ -9,6 +9,11 @@
 #include "dir.h"
 #include "fsmonitor.h"
 
+struct modify_index_context {
+	struct index_state *write;
+	struct pattern_list *pl;
+};
+
 static struct cache_entry *construct_sparse_dir_entry(
 				struct index_state *istate,
 				const char *sparse_dir,

@@ -231,18 +236,41 @@ static int add_path_to_index(const struct object_id *oid,
 			     struct strbuf *base, const char *path,
 			     unsigned int mode, void *context)
 {
-	struct index_state *istate = (struct index_state *)context;
+	struct modify_index_context *ctx = (struct modify_index_context *)context;
 	struct cache_entry *ce;
 	size_t len = base->len;
 
-	if (S_ISDIR(mode))
-		return READ_TREE_RECURSIVE;
+	if (S_ISDIR(mode)) {
+		int dtype;
+		size_t baselen = base->len;
+		if (!ctx->pl)
+			return READ_TREE_RECURSIVE;
 
-	strbuf_addstr(base, path);
+		/*
+		 * Have we expanded to a point outside of the sparse-checkout?
+		 */
+		strbuf_addstr(base, path);
+		strbuf_add(base, "/-", 2);
+
+		if (path_matches_pattern_list(base->buf, base->len,
+					      NULL, &dtype,
+					      ctx->pl, ctx->write)) {
+			strbuf_setlen(base, baselen);
+			return READ_TREE_RECURSIVE;
+		}
 
-	ce = make_cache_entry(istate, mode, oid, base->buf, 0, 0);
+		/*
+		 * The path "{base}{path}/" is a sparse directory. Create the correct
+		 * name for inserting the entry into the index.
+		 */
+		strbuf_setlen(base, base->len - 1);
+	} else {
+		strbuf_addstr(base, path);
+	}
+
+	ce = make_cache_entry(ctx->write, mode, oid, base->buf, 0, 0);
 	ce->ce_flags |= CE_SKIP_WORKTREE | CE_EXTENDED;
-	set_index_entry(istate, istate->cache_nr++, ce);
+	set_index_entry(ctx->write, ctx->write->cache_nr++, ce);
 
 	strbuf_setlen(base, len);
 	return 0;

@@ -254,6 +282,7 @@ void expand_to_pattern_list(struct index_state *istate,
 	int i;
 	struct index_state *full;
 	struct strbuf base = STRBUF_INIT;
+	struct modify_index_context ctx;
 
 	/*
 	 * If the index is already full, then keep it full. We will convert

@@ -294,6 +323,9 @@ void expand_to_pattern_list(struct index_state *istate,
 	full->cache_nr = 0;
 	ALLOC_ARRAY(full->cache, full->cache_alloc);
 
+	ctx.write = full;
+	ctx.pl = pl;
+
 	for (i = 0; i < istate->cache_nr; i++) {
 		struct cache_entry *ce = istate->cache[i];
 		struct tree *tree;

@@ -319,7 +351,7 @@ void expand_to_pattern_list(struct index_state *istate,
 		strbuf_add(&base, ce->name, strlen(ce->name));
 
 		read_tree_at(istate->repo, tree, &base, &ps,
-			     add_path_to_index, full);
+			     add_path_to_index, &ctx);
 
 		/* free directory entries. full entries are re-used */
 		discard_cache_entry(ce);

gitgitgadget

UNDECIDED can only be returned when not in cone mode. We are in cone mode when this helper is used.

The '+ "/-"' is there to give us an example file path for "<path>" as a directory. This is specifically because path_matches_pattern_list() checks the parent directories for matches, expecting the input to be a file name.

This could use a comment. I'm thinking...

/*
* Have we expanded to a point outside of the sparse-checkout? *
* Artificially pad the path name with a slash "/" to
* indicate it as a directory, and add an arbitrary file
* name ("-") so we can consider base->buf as a file name
* to match against the cone-mode patterns.
*
* If we compared just "path", then we would expand more
* than we should. Since every file at root is always
* included, we would expand every directory at root at
* least one level deep instead of using sparse directory
* entries.
*/

Thanks for your careful read. Hopefully my explanation of the "/-" thing helps.

Thanks,
-Stolee

From: Derrick Stolee <[email protected]>

To complete the implementation of expand_to_pattern_list(), we need to detect when a sparse directory entry should remain sparse. This avoids a full expansion, so we now need to use the PARTIALLY_SPARSE mode to indicate this state.

There still are no callers to this method, but we will add one in the next change.

---
 sparse-index.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

index 73b82e5017b..a65169030a2 100644
@@ -297,8 +297,24 @@ void expand_to_pattern_list(struct index_state *istate,
 	 * continue. A NULL pattern set indicates a full expansion to a
 	 * full index.
 	 */
-	if (pl && !pl->use_cone_patterns)
+	if (pl && !pl->use_cone_patterns) {
 		pl = NULL;
+	} else {
+		/*
+		 * We might contract file entries into sparse-directory
+		 * entries, and for that we will need the cache tree to
+		 * be recomputed.
+		 */
+		cache_tree_free(&istate->cache_tree);
+
+		/*
+		 * If there is a problem creating the cache tree, then we
+		 * need to expand to a full index since we cannot satisfy
+		 * the current request as a sparse index.
+		 */
+		if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
+			pl = NULL;
+	}
 
 	if (!istate->repo)
 		istate->repo = the_repository;

@@ -317,8 +333,14 @@ void expand_to_pattern_list(struct index_state *istate,
 	full = xcalloc(1, sizeof(struct index_state));
 	memcpy(full, istate, sizeof(struct index_state));
 
+	/*
+	 * This slightly-misnamed 'full' index might still be sparse if we
+	 * are only modifying the list of sparse directories. This hinges
+	 * on whether we have a non-NULL pattern list.
+	 */
+	full->sparse_index = pl ? PARTIALLY_SPARSE : COMPLETELY_FULL;
+
 	/* then change the necessary things */
-	full->sparse_index = 0;
 	full->cache_alloc = (3 * istate->cache_alloc) / 2;
 	full->cache_nr = 0;
 	ALLOC_ARRAY(full->cache, full->cache_alloc);

@@ -330,11 +352,22 @@ void expand_to_pattern_list(struct index_state *istate,
 		struct cache_entry *ce = istate->cache[i];
 		struct tree *tree;
 		struct pathspec ps;
+		int dtype;
 
 		if (!S_ISSPARSEDIR(ce->ce_mode)) {
 			set_index_entry(full, full->cache_nr++, ce);
 			continue;
 		}
+
+		/* We now have a sparse directory entry. Should we expand? */
+		if (pl &&
+		    path_matches_pattern_list(ce->name, ce->ce_namelen,
+					      NULL, &dtype,
+					      pl, istate) == NOT_MATCHED) {
+			set_index_entry(full, full->cache_nr++, ce);
+			continue;
+		}
+
 		if (!(ce->ce_flags & CE_SKIP_WORKTREE))
 			warning(_("index entry is a directory, but not sparse (%08x)"),
 				ce->ce_flags);

@@ -360,7 +393,7 @@ void expand_to_pattern_list(struct index_state *istate,
 	/* Copy back into original index. */
 	memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
 	memcpy(&istate->dir_hash, &full->dir_hash, sizeof(full->dir_hash));
-	istate->sparse_index = 0;
+	istate->sparse_index = pl ? PARTIALLY_SPARSE : COMPLETELY_FULL;
 	free(istate->cache);
 	istate->cache = full->cache;
 	istate->cache_nr = full->cache_nr;

@@ -374,7 +407,7 @@ void expand_to_pattern_list(struct index_state *istate,
 
 	/* Clear and recompute the cache-tree */
 	cache_tree_free(&istate->cache_tree);
-	cache_tree_update(istate, 0);
+	cache_tree_update(istate, WRITE_TREE_MISSING_OK);
 
 	trace2_region_leave("index",
 			    pl ? "expand_to_pattern_list" : "ensure_full_index",

gitgitgadget

You are correct that conflicts outside of the sparse-checkout cone will cause index expansion. That happens during the 'git merge' command, but the index will continue to fail to collapse as long as those conflicts still exist in the index.

When there are conflicts like this during the merge, then the index expansion is not as large of a portion of the command as normal, because the conflict resolution also takes some time to compute. The commands afterwards do take longer purely because of the expanded index.

However, this state is also not as common as you might think. If a user has a sparse-checkout cone specified, then they are unlikely to change files outside of the sparse-checkout cone. They would not be the reason that those files have a conflict. The conflicts would exist only if they are merging branches that had conflicts outside of the cone. Typically, any merge of external changes like this are of the form of "git pull" or "git rebase", in which case the conflicts are still "local" to the developer's changes.

You are right that there is additional work that could be done here, specifically allowing the cache tree to partially succeed and use the successfully generated trees to create sparse directory entries where possible. This was not viable before because we lacked the "partially expanded" index state. This series establishes the necessary vocabulary to do such an improvement later.

Both of these additions of WRITE_TREE_MISSING_OK are not needed. I think I added them in an earlier version, thinking they were needed due to something in the Scalar functional tests. I confirmed just now that they are not needed for that. I will remove them.

Thanks,
-Stolee

As I went to remove these from sparse-index.c, I found another that exists, but for good reason. See 8a96b9d0a (sparse-index: use WRITE_TREE_MISSING_OK, 2021-09-08), which explains that that instance needs the flag because it could be used during 'git add'.

It still isn't necessary in the instances being added here, so I will remove them.

Thanks,
-Stolee

Hmph, re-reading that explanation, it appears to me that it is working around a lack of another option that could be useful in such a situation, namely, "update the cache tree, and if a tree object is missing then create one locally; do not bother asking any promisor remote". I am reasonably sure that back when I invented missing-ok there wasn't any such thing as "promisor remote" or "lazy fetch", and it sounds like those who added "promissor remote" broke the cache-tree subsystem by introducing calls to fetch from elsewhere?

How does a normal "new object creation" codepath work when promisor remotes exist? Does write_object_file() first ask if any promisor remote have that object and fetch before creating one locally? That sounds absurd (i.e. if we have data to create locally why ask others if they have one already?). Why should cache-tree behave any differently?

All of the above are mere observations on changes that have nothing to do with the change in this series, but cache_tree_update() knowing about promisor remotes feels serious breakage to me.

OK.

I was imagining a situation more like "tech-writers only have Documentation/ inside the cone of interest, attempt a pull from somebody else, have conflicts inside Documentation/, but everything else could be resolved cleanly without expanding the index". If the puller's tree is based on the pristine upstream release tag, and the pullee's tree is based on a slightly newer version of upstream snapshot, everything that happened outside Documentation/ in their trees would fast-forward, so such a merge wouldn't have to expand directories like "builtin/" or "contrib/" in the index and instead can merge at the tree level, right?

On the other hand, ...

... you seem to be talking about the opposite case (e.g. in the above paragraph), where a conflict happens outside the cone of interest of the person who is making a merge. So, I am a bit puzzled.

Hm. We must be getting mixed up with each other. Let me try again from the beginning.

When the conflict happens inside of the sparse-checkout cone, then the sparse index is not expanded. This is checked by the test 'sparse-index is not expanded: merge conflict in cone' in t1092.

Most merges get to "fast forward" changes that are outside of the sparse-checkout cone because the only interesting changes that could lead to a conflict are those created by the current user (and hence within the sparse-checkout cone).

So, the typical case of a tech writer only editing "Documentation/" should only see conflicts within "Documentation/".

The case where we would see conflicts outside of the cone include cases where long-lived branches are being merged by someone with a small cone. I can imagine an automated process using an empty sparse-checkout cone to occasionally merge a "deployed" and a "develop" branch, and it gets conflicts when someone ships a hotfix directly to "deployed" without first going through "develop". Any conflict is likely to cause index expansion in this case.

Let's re-introduce the patch section we are talking about:

+ if (pl && !pl->use_cone_patterns) {
pl = NULL;
+ } else {
+ /*
+ * We might contract file entries into sparse-directory
+ * entries, and for that we will need the cache tree to
+ * be recomputed.
+ */
+ cache_tree_free(&istate->cache_tree);
+
+ /*
+ * If there is a problem creating the cache tree, then we
+ * need to expand to a full index since we cannot satisfy
+ * the current request as a sparse index.
+ */
+ if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
+ pl = NULL;
+ }

If a user is in a conflict state and modifies their sparse-checkout cone, then we will hit this "recompute the cache-tree" state, fail, and cause full index expansion. I think that combination (have a conflict AND modify sparse-checkout cone) is rare enough to not optimize for (yet).

Does that make the situation more clear?

Thanks,
-Stolee

Yes. "AND modify sparse-checkout cone" part was what I was missing. I didn't see it because it wasn't there at all in the code that was removed or added---it comes from the fact that the user is running the "sparse-checkout" command in the first place, and that was what I missed.

Thanks.

From: Derrick Stolee <[email protected]>

The sparse-checkout builtin is almost completely integrated with the sparse index, allowing the sparse-checkout boundary to be modified without expanding a sparse index to a full one. Add a test to p2000-sparse-operations.sh that adds a directory to the sparse-checkout definition, then removes it. Using both operations is important to ensure that the operation is doing the same work in each repetition as well as leaving the test repo in a good state for later tests.

---
 t/perf/p2000-sparse-operations.sh | 1 +
 1 file changed, 1 insertion(+)

index 382716cfca9..ce5cfac5714 100755
@@ -110,6 +110,7 @@ test_perf_on_all git add -A
 test_perf_on_all git add .
 test_perf_on_all git commit -a -m A
 test_perf_on_all git checkout -f -
+test_perf_on_all "git sparse-checkout add f2/f3/f1 && git sparse-checkout set $SPARSE_CONE"
 test_perf_on_all git reset
 test_perf_on_all git reset --hard
 test_perf_on_all git reset -- does-not-exist

gitgitgadget

From: Derrick Stolee <[email protected]>

When modifying the sparse-checkout definition, the sparse-checkout builtin calls update_sparsity() to modify the SKIP_WORKTREE bits of all cache entries in the index. Before, we needed the index to be fully expanded in order to ensure we had the full list of files necessary that match the new patterns.

Insert a call to reset_sparse_directories() that expands sparse directories that are within the new pattern list, but only far enough that every necessary file path now exists as a cache entry. The remaining logic within update_sparsity() will modify the SKIP_WORKTREE bits appropriately.

This allows us to disable command_requires_full_index within the sparse-checkout builtin. Add tests that demonstrate that we are not expanding to a full index unnecessarily.

We can see the improved performance in the p2000 test script:

Test HEAD~1 HEAD
------------------------------------------------------------------------

2000.24: git ... (sparse-v3)   2.14(1.55+0.58)   1.57(1.03+0.53) -26.6%
2000.25: git ... (sparse-v4)   2.20(1.62+0.57)   1.58(0.98+0.59) -28.2%

These reductions of 26-28% are small compared to most examples, but the time is dominated by writing a new copy of the base repository to the worktree and then deleting it again. The fact that the previous index expansion was such a large portion of the time is telling how important it is to complete this sparse index integration.

---
 builtin/sparse-checkout.c                |  3 +++
 t/t1092-sparse-checkout-compatibility.sh | 25 ++++++++++++++++++++++++
 unpack-trees.c                           |  4 ++++
 3 files changed, 32 insertions(+)

index cbff6ad00b0..0157b292b36 100644
@@ -937,6 +937,9 @@ int cmd_sparse_checkout(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config, NULL);
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	if (argc > 0) {
 		if (!strcmp(argv[0], "list"))
 			return sparse_checkout_list(argc, argv);

index 785820f9fd5..73f4cf47314 100755
@@ -1584,6 +1584,31 @@ test_expect_success 'ls-files' '
 	ensure_not_expanded ls-files --sparse
 '
 
+test_expect_success 'sparse index is not expanded: sparse-checkout' '
+	init_repos &&
+
+	ensure_not_expanded sparse-checkout set deep/deeper2 &&
+	ensure_not_expanded sparse-checkout set deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set deep &&
+	ensure_not_expanded sparse-checkout add folder1 &&
+	ensure_not_expanded sparse-checkout set deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set folder2 &&
+
+	# Demonstrate that the checks that "folder1/a" is a file
+	# do not cause a sparse-index expansion (since it is in the
+	# sparse-checkout cone).
+	echo >>sparse-index/folder2/a &&
+	git -C sparse-index add folder2/a &&
+
+	ensure_not_expanded sparse-checkout add folder1 &&
+
+	# Skip checks here, since deep/deeper1 is inside a sparse directory
+	# that must be expanded to check whether `deep/deeper1` is a file
+	# or not.
+	ensure_not_expanded sparse-checkout set --skip-checks deep/deeper1 &&
+	ensure_not_expanded sparse-checkout set
+'
+
 # NEEDSWORK: a sparse-checkout behaves differently from a full checkout
 # in this scenario, but it shouldn't.
 test_expect_success 'reset mixed and checkout orphan' '

index 7f528d35cc2..9745e0dfc34 100644
@@ -18,6 +18,7 @@
 #include "promisor-remote.h"
 #include "entry.h"
 #include "parallel-checkout.h"
+#include "sparse-index.h"
 
 /*
  * Error messages expected by scripts out of plumbing commands such as

@@ -2018,6 +2019,9 @@ enum update_sparsity_result update_sparsity(struct unpack_trees_options *o)
 			goto skip_sparse_checkout;
 	}
 
+	/* Expand sparse directories as needed */
+	expand_to_pattern_list(o->src_index, o->pl);
+
 	/* Set NEW_SKIP_WORKTREE on existing entries. */
 	mark_all_ce_unused(o->src_index);
 	mark_new_skip_worktree(o->pl, o->src_index, 0,

gitgitgadget

This series is based on ds/sparse-colon-path.

This series integrates the 'git sparse-checkout' builtin with the sparse index. This is the last integration that we fast-tracked into the microsoft/git fork. After this, we have no work in flight that would conflict with a Google Summer of Code project in this area.

The tricky part about the sparse-checkout builtin is that we actually do need to expand the index when growing the sparse-checkout boundary. The trick is to expand it only as far as we need it, and then ensure that we collapse any removed directories before the command completes.

To do this, we introduce a concept of a "partially expanded" index. In fact, we break the boolean sparse_index member into an enum with three states:

* INDEX_EXPANDED (0): No sparse directories exist.

* INDEX_COLLAPSED: Sparse directories may exist. Files outside the sparse-checkout cone are reduced to sparse directory entries whenever possible.

* INDEX_PARTIALLY_SPARSE: Sparse directories may exist. Some file entries outside the sparse-checkout cone may exist. Running convert_to_sparse() may further reduce those files to sparse directory entries.

Most of the patches in this series focus on introducing this enum and carefully converting previous uses of the boolean to use the enum. Some additional work is required to refactor ensure_full_index() into a new expand_index() method, as they are doing essentially the same thing, but with different scopes.

The result is improved performance on the sparse-checkout builtin as demonstrated in a new p2000-sparse-operations.sh performance test:

Test HEAD~1 HEAD
================

2000.24: git sparse-checkout ... (sparse-v3) 2.14(1.55+0.58) 1.57(1.03+0.53) -26.6% 2000.25: git sparse-checkout ... (sparse-v4) 2.20(1.62+0.57) 1.58(0.98+0.59) -28.2%

The improvement here is less dramatic because the operation is dominated by writing and deleting a lot of files in the worktree. A repeated no-op operation such as git sparse-checkout set $SPARSE_CONE would show a greater improvement, but is less interesting since it could gain that improvement without satisfying the "hard" parts of this builtin.

I specifically chose how to update the tests in t1092 and p2000 to avoid conflicts with Victoria's 'git stash' work.

Updates in v3
=============

* expand_to_pattern_list() is renamed to expand_index().

* The enum values are renamed to be less ambiguous.

* Use a local variable to store the trace2 region label.

* A tail-recursive method is converted to an iterative one.

* Comments are added.

* WRITE_MISSING_TREE_OK flags are removed as unnecessary.

Updates in v2
=============

* Typo fixes.
* Two patches are added to the start to (a) refactor existing sparse index content tests, and (b) add new sparse index content tests with additional scenarios.
* Use NOT_MATCHED directly instead of implicitly allowing UNDECIDED when matching in cone mode.

Thanks, -Stolee

Derrick Stolee (10):
t1092: refactor 'sparse-index contents' test
t1092: stress test 'git sparse-checkout set'
sparse-index: create expand_index()
sparse-index: introduce partially-sparse indexes
cache-tree: implement cache_tree_find_path()
sparse-checkout: --no-sparse-index needs a full index
sparse-index: partially expand directories
sparse-index: complete partial expansion
p2000: add test for 'git sparse-checkout [add|set]'
sparse-checkout: integrate with sparse index

 builtin/sparse-checkout.c                |   8 +-
 cache-tree.c                             |  27 +++++
 cache-tree.h                             |   2 +
 cache.h                                  |  33 ++++--
 read-cache.c                             |   6 +-
 sparse-index.c                           | 132 ++++++++++++++++++++---
 sparse-index.h                           |  13 +++
 t/perf/p2000-sparse-operations.sh        |   1 +
 t/t1092-sparse-checkout-compatibility.sh |  95 ++++++++++++----
 unpack-trees.c                           |   4 +
 10 files changed, 275 insertions(+), 46 deletions(-)

base-commit: 124b05b23005437fa5fb91863bde2a8f5840e164
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1208%2Fderrickstolee%2Fsparse-index%2Fsparse-checkout-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1208/derrickstolee/sparse-index/sparse-checkout-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1208

Range-diff vs v2:

  1:  f2960747ed8 =  1:  f2960747ed8 t1092: refactor 'sparse-index contents' test
  2:  5030eeecf4f =  2:  5030eeecf4f t1092: stress test 'git sparse-checkout set'
  3:  d15338573e5 !  3:  44b0549a288 sparse-index: create expand_to_pattern_list()

@@ Metadata
Author: Derrick Stolee <[email protected]>

## Commit message ##
- sparse-index: create expand_to_pattern_list()
+ sparse-index: create expand_index()

This is the first change in a series to allow modifying the sparse-checkout pattern set without expanding a sparse index to a full
@@ Commit message

We already have logic in ensure_full_index() that expands the index entries, so we will use that as our base. Create a new method,
- expand_to_pattern_list(), which takes a pattern list, but for now mostly
- ignores it. The current implementation is only correct when the pattern
- list is NULL as that does the same as ensure_full_index(). In fact,
- ensure_full_index() is converted to a shim over
- expand_to_pattern_list().
+ expand_index(), which takes a pattern list, but for now mostly ignores
+ it. The current implementation is only correct when the pattern list is
+ NULL as that does the same as ensure_full_index(). In fact,
+ ensure_full_index() is converted to a shim over expand_index().

- A future update will actually implement expand_to_pattern_list() to its
- full capabilities. For now, it is created and documented.
+ A future update will actually implement expand_index() to its full
+ capabilities. For now, it is created and documented.

@@ sparse-index.c: static int add_path_to_index(const struct object_id *oid,
}

-void ensure_full_index(struct index_state *istate)
-+void expand_to_pattern_list(struct index_state *istate,
-+ struct pattern_list *pl)
++void expand_index(struct index_state *istate, struct pattern_list *pl)
{
int i;
struct index_state *full;
struct strbuf base = STRBUF_INIT;
++ const char *tr_region;

+ /*
+ * If the index is already full, then keep it full. We will convert
@@ sparse-index.c: static int add_path_to_index(const struct object_id *oid,
+ * This is used by test cases, but also helps to differentiate the
+ * two cases.
+ */
-+ trace2_region_enter("index",
-+ pl ? "expand_to_pattern_list" : "ensure_full_index",
-+ istate->repo);
++ tr_region = pl ? "expand_index" : "ensure_full_index";
++ trace2_region_enter("index", tr_region, istate->repo);

/* initialize basics of new index */
full = xcalloc(1, sizeof(struct index_state));
@@ sparse-index.c: void ensure_full_index(struct index_state *istate)
cache_tree_update(istate, 0);

- trace2_region_leave("index", "ensure_full_index", istate->repo);
-+ trace2_region_leave("index",
-+ pl ? "expand_to_pattern_list" : "ensure_full_index",
-+ istate->repo);
++ trace2_region_leave("index", tr_region, istate->repo);
+}
+
+void ensure_full_index(struct index_state *istate) +{
-+ expand_to_pattern_list(istate, NULL);
++ expand_index(istate, NULL);
}

void ensure_correct_sparsity(struct index_state *istate)
@@ sparse-index.h: void expand_to_path(struct index_state *istate,
+ * If the pattern list is NULL or does not use cone mode patterns, then the
+ * index is expanded to a full index.
+ */
-+void expand_to_pattern_list(struct index_state *istate,
-+ struct pattern_list *pl);
++void expand_index(struct index_state *istate, struct pattern_list *pl);
+
#endif
4: 269c206c331 ! 4: 8a459d6c67d sparse-index: introduce partially-sparse indexes

     @@ Commit message
          For now, convert the single-bit member 'sparse_index' in 'struct
          index_state' to be a an 'enum sparse_index_mode' with three modes:
      
     -    * COMPLETELY_FULL (0): No sparse directories exist.
     +    * INDEX_EXPANDED (0): No sparse directories exist. This is always the
     +      case for repositories that do not use cone-mode sparse-checkout.
      
     -    * COMPLETELY_SPARSE (1): Sparse directories may exist. Files outside the
     +    * INDEX_COLLAPSED: Sparse directories may exist. Files outside the
            sparse-checkout cone are reduced to sparse directory entries whenever
            possible.
      
     -    * PARTIALLY_SPARSE (2): Sparse directories may exist. Some file entries
     -      outside the sparse-checkout cone may exist. Running
     +    * INDEX_PARTIALLY_SPARSE: Sparse directories may exist. Some file
     +      entries outside the sparse-checkout cone may exist. Running
            convert_to_sparse() may further reduce those files to sparse directory
            entries.
      
          The main reason to store this extra information is to allow
          convert_to_sparse() to short-circuit when the index is already in
     -    COMPLETELY_SPARSE mode but to actually do the necessary work when in
     -    PARTIALLY_SPARSE mode.
     +    INDEX_EXPANDED mode but to actually do the necessary work when in
     +    INDEX_PARTIALLY_SPARSE mode.
      
     -    The PARTIALLY_SPARSE mode will be used in an upcoming change.
     +    The INDEX_PARTIALLY_SPARSE mode will be used in an upcoming change.
      
          Signed-off-by: Derrick Stolee <[email protected]>
      
     @@ builtin/sparse-checkout.c: static void clean_tracked_sparse_directories(struct r
       	 * conflicted entries or submodules.
       	 */
      -	if (!r->index->sparse_index) {
     -+	if (r->index->sparse_index == COMPLETELY_FULL) {
     ++	if (r->index->sparse_index == INDEX_EXPANDED) {
       		/*
       		 * If something, such as a merge conflict or other concern,
       		 * prevents us from converting to a sparse index, then do
     @@ cache.h: struct untracked_cache;
       
      +enum sparse_index_mode {
      +	/*
     -+	 * COMPLETELY_FULL: there are no sparse directories
     -+	 * in the index at all.
     ++	 * There are no sparse directories in the index at all.
     ++	 *
     ++	 * Repositories that don't use cone-mode sparse-checkout will
     ++	 * always have their indexes in this mode.
      +	 */
     -+	COMPLETELY_FULL = 0,
     ++	INDEX_EXPANDED = 0,
      +
      +	/*
     -+	 * COLLAPSED: the index has already been collapsed to sparse
     -+	 * directories whereever possible.
     ++	 * The index has already been collapsed to sparse directories
     ++	 * whereever possible.
      +	 */
     -+	COLLAPSED = 1,
     ++	INDEX_COLLAPSED,
      +
      +	/*
     -+	 * PARTIALLY_SPARSE: the sparse directories that exist are
     -+	 * outside the sparse-checkout boundary, but it is possible
     -+	 * that some file entries could collapse to sparse directory
     -+	 * entries.
     ++	 * The sparse directories that exist are outside the
     ++	 * sparse-checkout boundary, but it is possible that some file
     ++	 * entries could collapse to sparse directory entries.
      +	 */
     -+	PARTIALLY_SPARSE = 2,
     ++	INDEX_PARTIALLY_SPARSE,
      +};
      +
       struct index_state {
     @@ read-cache.c: static const char *alternate_index_output;
       {
       	if (S_ISSPARSEDIR(ce->ce_mode))
      -		istate->sparse_index = 1;
     -+		istate->sparse_index = COLLAPSED;
     ++		istate->sparse_index = INDEX_COLLAPSED;
       
       	istate->cache[nr] = ce;
       	add_name_hash(istate, ce);
     @@ read-cache.c: static int read_index_extension(struct index_state *istate,
       	case CACHE_EXT_SPARSE_DIRECTORIES:
       		/* no content, only an indicator */
      -		istate->sparse_index = 1;
     -+		istate->sparse_index = COLLAPSED;
     ++		istate->sparse_index = INDEX_COLLAPSED;
       		break;
       	default:
       		if (*ext < 'A' || 'Z' < *ext)
     @@ read-cache.c: static int do_write_locked_index(struct index_state *istate, struc
       {
       	int ret;
      -	int was_full = !istate->sparse_index;
     -+	int was_full = istate->sparse_index == COMPLETELY_FULL;
     ++	int was_full = istate->sparse_index == INDEX_EXPANDED;
       
       	ret = convert_to_sparse(istate, 0);
       
     @@ sparse-index.c: int convert_to_sparse(struct index_state *istate, int flags)
       	 * cannot be converted to sparse, do not convert.
       	 */
      -	if (istate->sparse_index || !istate->cache_nr ||
     -+	if (istate->sparse_index == COLLAPSED || !istate->cache_nr ||
     ++	if (istate->sparse_index == INDEX_COLLAPSED || !istate->cache_nr ||
       	    !is_sparse_index_allowed(istate, flags))
       		return 0;
       
     @@ sparse-index.c: int convert_to_sparse(struct index_state *istate, int flags)
       	FREE_AND_NULL(istate->fsmonitor_last_update);
       
      -	istate->sparse_index = 1;
     -+	istate->sparse_index = COLLAPSED;
     ++	istate->sparse_index = INDEX_COLLAPSED;
       	trace2_region_leave("index", "convert_to_sparse", istate->repo);
       	return 0;
       }
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       	 * If the index is already full, then keep it full. We will convert
       	 * it to a sparse index on write, if possible.
       	 */
      -	if (!istate || !istate->sparse_index)
     -+	if (!istate || istate->sparse_index == COMPLETELY_FULL)
     ++	if (!istate || istate->sparse_index == INDEX_EXPANDED)
       		return;
       
       	/*
  5:  c977001c033 !  5:  9103584ed75 cache-tree: implement cache_tree_find_path()
     @@ Commit message
          path exists.
      
          The implementation is adapted from do_invalidate_path() which does a
     -    similar search but also modifies the nodes it finds along the way.
     +    similar search but also modifies the nodes it finds along the way. The
     +    method could be implemented simply using tail-recursion, but this while
     +    loop does the same thing.
      
          This new method is not currently used, but will be in an upcoming
          change.
      
     +    Helped-by: Junio C Hamano <[email protected]>
          Signed-off-by: Derrick Stolee <[email protected]>
      
       ## cache-tree.c ##
     @@ cache-tree.c: struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const
      +{
      +	const char *slash;
      +	int namelen;
     -+	struct cache_tree_sub *down;
     ++	struct cache_tree_sub it_sub = {
     ++		.cache_tree = it,
     ++	};
     ++	struct cache_tree_sub *down = &it_sub;
      +
     -+	if (!it)
     -+		return NULL;
     -+	slash = strchrnul(path, '/');
     -+	namelen = slash - path;
     -+	it->entry_count = -1;
     -+	if (!*slash) {
     -+		int pos;
     -+		pos = cache_tree_subtree_pos(it, path, namelen);
     -+		if (0 <= pos)
     -+			return it->down[pos]->cache_tree;
     -+		return NULL;
     ++	while (down) {
     ++		slash = strchrnul(path, '/');
     ++		namelen = slash - path;
     ++		down->cache_tree->entry_count = -1;
     ++		if (!*slash) {
     ++			int pos;
     ++			pos = cache_tree_subtree_pos(down->cache_tree, path, namelen);
     ++			if (0 <= pos)
     ++				return down->cache_tree->down[pos]->cache_tree;
     ++			return NULL;
     ++		}
     ++		down = find_subtree(it, path, namelen, 0);
     ++		path = slash + 1;
      +	}
     -+	down = find_subtree(it, path, namelen, 0);
     -+	if (down)
     -+		return cache_tree_find_path(down->cache_tree, slash + 1);
     ++
      +	return NULL;
      +}
      +
  6:  e42463de0d2 =  6:  75ecb579a9f sparse-checkout: --no-sparse-index needs a full index
  7:  346c56bf256 !  7:  310e59d9f0e sparse-index: partially expand directories
     @@ sparse-index.c: static int add_path_to_index(const struct object_id *oid,
      -	strbuf_addstr(base, path);
      +		/*
      +		 * Have we expanded to a point outside of the sparse-checkout?
     ++		 *
     ++		 * Artificially pad the path name with a slash "/" to
     ++		 * indicate it as a directory, and add an arbitrary file
     ++		 * name ("-") so we can consider base->buf as a file name
     ++		 * to match against the cone-mode patterns.
     ++		 *
     ++		 * If we compared just "path", then we would expand more
     ++		 * than we should. Since every file at root is always
     ++		 * included, we would expand every directory at root at
     ++		 * least one level deep instead of using sparse directory
     ++		 * entries.
      +		 */
      +		strbuf_addstr(base, path);
      +		strbuf_add(base, "/-", 2);
     @@ sparse-index.c: static int add_path_to_index(const struct object_id *oid,
       
       	strbuf_setlen(base, len);
       	return 0;
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     - 	int i;
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       	struct index_state *full;
       	struct strbuf base = STRBUF_INIT;
     + 	const char *tr_region;
      +	struct modify_index_context ctx;
       
       	/*
       	 * If the index is already full, then keep it full. We will convert
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       	full->cache_nr = 0;
       	ALLOC_ARRAY(full->cache, full->cache_alloc);
       
     @@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
       	for (i = 0; i < istate->cache_nr; i++) {
       		struct cache_entry *ce = istate->cache[i];
       		struct tree *tree;
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       		strbuf_add(&base, ce->name, strlen(ce->name));
       
       		read_tree_at(istate->repo, tree, &base, &ps,
  8:  ed640e3645b !  8:  b3cbfd3f136 sparse-index: complete partial expansion
     @@ Commit message
          Signed-off-by: Derrick Stolee <[email protected]>
      
       ## sparse-index.c ##
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       	 * continue. A NULL pattern set indicates a full expansion to a
       	 * full index.
       	 */
     @@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
      +		 * need to expand to a full index since we cannot satisfy
      +		 * the current request as a sparse index.
      +		 */
     -+		if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
     ++		if (cache_tree_update(istate, 0))
      +			pl = NULL;
      +	}
       
       	if (!istate->repo)
       		istate->repo = the_repository;
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       	full = xcalloc(1, sizeof(struct index_state));
       	memcpy(full, istate, sizeof(struct index_state));
       
     @@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
      +	 * are only modifying the list of sparse directories. This hinges
      +	 * on whether we have a non-NULL pattern list.
      +	 */
     -+	full->sparse_index = pl ? PARTIALLY_SPARSE : COMPLETELY_FULL;
     ++	full->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;
      +
       	/* then change the necessary things */
      -	full->sparse_index = 0;
       	full->cache_alloc = (3 * istate->cache_alloc) / 2;
       	full->cache_nr = 0;
       	ALLOC_ARRAY(full->cache, full->cache_alloc);
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       		struct cache_entry *ce = istate->cache[i];
       		struct tree *tree;
       		struct pathspec ps;
     @@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
       		if (!(ce->ce_flags & CE_SKIP_WORKTREE))
       			warning(_("index entry is a directory, but not sparse (%08x)"),
       				ce->ce_flags);
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     +@@ sparse-index.c: void expand_index(struct index_state *istate, struct pattern_list *pl)
       	/* Copy back into original index. */
       	memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
       	memcpy(&istate->dir_hash, &full->dir_hash, sizeof(full->dir_hash));
      -	istate->sparse_index = 0;
     -+	istate->sparse_index = pl ? PARTIALLY_SPARSE : COMPLETELY_FULL;
     ++	istate->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;
       	free(istate->cache);
       	istate->cache = full->cache;
       	istate->cache_nr = full->cache_nr;
     -@@ sparse-index.c: void expand_to_pattern_list(struct index_state *istate,
     - 
     - 	/* Clear and recompute the cache-tree */
     - 	cache_tree_free(&istate->cache_tree);
     --	cache_tree_update(istate, 0);
     -+	cache_tree_update(istate, WRITE_TREE_MISSING_OK);
     - 
     - 	trace2_region_leave("index",
     - 			    pl ? "expand_to_pattern_list" : "ensure_full_index",
  9:  089ab086f58 =  9:  aa3bdcf705c p2000: add test for 'git sparse-checkout [add|set]'
 10:  ad9ed6973d5 ! 10:  11728619120 sparse-checkout: integrate with sparse index
     @@ unpack-trees.c: enum update_sparsity_result update_sparsity(struct unpack_trees_
       	}
       
      +	/* Expand sparse directories as needed */
     -+	expand_to_pattern_list(o->src_index, o->pl);
     ++	expand_index(o->src_index, o->pl);
      +
       	/* Set NEW_SKIP_WORKTREE on existing entries. */
       	mark_all_ce_unused(o->src_index);

gitgitgadget

From: Derrick Stolee <[email protected]>

Before expanding this test with more involved cases, first extract the repeated logic into a new test_sparse_checkout_set helper. This helper checks that 'git sparse-checkout set ...' succeeds and then verifies that certain directories have sparse directory entries in the sparse index. It also verifies that the in-cone directories are _not_ sparse directory entries in the sparse index.

---
 t/t1092-sparse-checkout-compatibility.sh | 53 ++++++++++++++++--------
 1 file changed, 35 insertions(+), 18 deletions(-)

index 93bcfd20bbc..e7c0ae9b953 100755
@@ -205,36 +205,53 @@ test_sparse_unstaged () {
 	done
 }
 
-test_expect_success 'sparse-index contents' '
-	init_repos &&
-
+# Usage: test_sprase_checkout_set "<c1> ... <cN>" "<s1> ... <sM>"
+# Verifies that "git sparse-checkout set <c1> ... <cN>" succeeds and
+# leaves the sparse index in a state where <s1> ... <sM> are sparse
+# directories (and <c1> ... <cN> are not).
+test_sparse_checkout_set () {
+	CONE_DIRS=$1 &&
+	SPARSE_DIRS=$2 &&
+	git -C sparse-index sparse-checkout set $CONE_DIRS &&
 	git -C sparse-index ls-files --sparse --stage >cache &&
-	for dir in folder1 folder2 x
+
+	# Check that the directories outside of the sparse-checkout cone
+	# have sparse directory entries.
+	for dir in $SPARSE_DIRS
 	do
 		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
 		grep "040000 $TREE 0	$dir/" cache \
 			|| return 1
 	done &&
 
-	git -C sparse-index sparse-checkout set folder1 &&
-
-	git -C sparse-index ls-files --sparse --stage >cache &&
-	for dir in deep folder2 x
+	# Check that the directories in the sparse-checkout cone
+	# are not sparse directory entries.
+	for dir in $CONE_DIRS
 	do
 		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
-		grep "040000 $TREE 0	$dir/" cache \
+		! grep "040000 $TREE 0	$dir/" cache \
 			|| return 1
-	done &&
+	done
+}
 
-	git -C sparse-index sparse-checkout set deep/deeper1 &&
+test_expect_success 'sparse-index contents' '
+	init_repos &&
 
-	git -C sparse-index ls-files --sparse --stage >cache &&
-	for dir in deep/deeper2 folder1 folder2 x
-	do
-		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
-		grep "040000 $TREE 0	$dir/" cache \
-			|| return 1
-	done &&
+	# Remove deep, add three other directories.
+	test_sparse_checkout_set \
+		"folder1 folder2 x" \
+		"before deep" &&
+
+	# Remove folder1, add deep
+	test_sparse_checkout_set \
+		"deep folder2 x" \
+		"before folder1" &&
+
+	# Replace deep with deep/deeper2 (dropping deep/deeper1)
+	# Add folder1
+	test_sparse_checkout_set \
+		"deep/deeper2 folder1 folder2 x" \
+		"before deep/deeper1" &&
 
 	# Disabling the sparse-index replaces tree entries with full ones
 	git -C sparse-index sparse-checkout init --no-sparse-index &&

gitgitgadget

From: Derrick Stolee <[email protected]>

The 'sparse-index contents' test checks that the sparse index has the correct set of sparse directories in the index after modifying the cone mode patterns using 'git sparse-checkout set'. Add to the coverage here by adding more complicated scenarios that were not previously tested.

In order to check paths that do not exist at HEAD, we need to modify the test_sparse_checkout_set helper slightly:

1. Add the --skip-checks argument to the 'set' command to avoid failures when passing paths that do not exist at HEAD.

2. When looking for the non-existence of sparse directories for the paths in $CONE_DIRS, allow the rev-list command to fail because the path does not exist at HEAD.

This allows us to add some interesting test cases.

---
 t/t1092-sparse-checkout-compatibility.sh | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

index e7c0ae9b953..785820f9fd5 100755
@@ -212,7 +212,7 @@ test_sparse_unstaged () {
 test_sparse_checkout_set () {
 	CONE_DIRS=$1 &&
 	SPARSE_DIRS=$2 &&
-	git -C sparse-index sparse-checkout set $CONE_DIRS &&
+	git -C sparse-index sparse-checkout set --skip-checks $CONE_DIRS &&
 	git -C sparse-index ls-files --sparse --stage >cache &&
 
 	# Check that the directories outside of the sparse-checkout cone

@@ -228,7 +228,9 @@ test_sparse_checkout_set () {
 	# are not sparse directory entries.
 	for dir in $CONE_DIRS
 	do
-		TREE=$(git -C sparse-index rev-parse HEAD:$dir) &&
+		# Allow TREE to not exist because
+		# $dir does not exist at HEAD.
+		TREE=$(git -C sparse-index rev-parse HEAD:$dir) ||
 		! grep "040000 $TREE 0	$dir/" cache \
 			|| return 1
 	done

@@ -253,6 +255,19 @@ test_expect_success 'sparse-index contents' '
 		"deep/deeper2 folder1 folder2 x" \
 		"before deep/deeper1" &&
 
+	# Replace deep/deeper2 with deep/deeper1
+	# Replace folder1 with folder1/0/0
+	# Replace folder2 with non-existent folder2/2/3
+	# Add non-existent "bogus"
+	test_sparse_checkout_set \
+		"bogus deep/deeper1 folder1/0/0 folder2/2/3 x" \
+		"before deep/deeper2 folder2/0" &&
+
+	# Drop down to only files at root
+	test_sparse_checkout_set \
+		"" \
+		"before deep folder1 folder2 x" &&
+
 	# Disabling the sparse-index replaces tree entries with full ones
 	git -C sparse-index sparse-checkout init --no-sparse-index &&
 	test_sparse_match git ls-files --stage --sparse

gitgitgadget

From: Derrick Stolee <[email protected]>

This is the first change in a series to allow modifying the sparse-checkout pattern set without expanding a sparse index to a full one in the process. Here, we focus on the problem of expanding the pattern set through a command like 'git sparse-checkout add <path>' which needs to create new index entries for the paths now being written to the worktree.

To achieve this, we need to be able to replace sparse directory entries with their contained files and subdirectories. Once this is complete, other code paths can discover those cache entries and write the corresponding files to disk before committing the index.

We already have logic in ensure_full_index() that expands the index entries, so we will use that as our base. Create a new method, expand_index(), which takes a pattern list, but for now mostly ignores it. The current implementation is only correct when the pattern list is NULL as that does the same as ensure_full_index(). In fact, ensure_full_index() is converted to a shim over expand_index().

A future update will actually implement expand_index() to its full capabilities. For now, it is created and documented.

---
 sparse-index.c | 32 +++++++++++++++++++++++++++++---
 sparse-index.h | 13 +++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)

index 8636af72de5..a11b5cf1314 100644
@@ -248,19 +248,40 @@ static int add_path_to_index(const struct object_id *oid,
 	return 0;
 }
 
-void ensure_full_index(struct index_state *istate)
+void expand_index(struct index_state *istate, struct pattern_list *pl)
 {
 	int i;
 	struct index_state *full;
 	struct strbuf base = STRBUF_INIT;
+	const char *tr_region;
 
+	/*
+	 * If the index is already full, then keep it full. We will convert
+	 * it to a sparse index on write, if possible.
+	 */
 	if (!istate || !istate->sparse_index)
 		return;
 
+	/*
+	 * If our index is sparse, but our new pattern set does not use
+	 * cone mode patterns, then we need to expand the index before we
+	 * continue. A NULL pattern set indicates a full expansion to a
+	 * full index.
+	 */
+	if (pl && !pl->use_cone_patterns)
+		pl = NULL;
+
 	if (!istate->repo)
 		istate->repo = the_repository;
 
-	trace2_region_enter("index", "ensure_full_index", istate->repo);
+	/*
+	 * A NULL pattern set indicates we are expanding a full index, so
+	 * we use a special region name that indicates the full expansion.
+	 * This is used by test cases, but also helps to differentiate the
+	 * two cases.
+	 */
+	tr_region = pl ? "expand_index" : "ensure_full_index";
+	trace2_region_enter("index", tr_region, istate->repo);
 
 	/* initialize basics of new index */
 	full = xcalloc(1, sizeof(struct index_state));

@@ -322,7 +343,12 @@ void ensure_full_index(struct index_state *istate)
 	cache_tree_free(&istate->cache_tree);
 	cache_tree_update(istate, 0);
 
-	trace2_region_leave("index", "ensure_full_index", istate->repo);
+	trace2_region_leave("index", tr_region, istate->repo);
+}
+
+void ensure_full_index(struct index_state *istate)
+{
+	expand_index(istate, NULL);
 }
 
 void ensure_correct_sparsity(struct index_state *istate)

index 633d4fb7e31..b1f2cdbb164 100644
@@ -23,4 +23,17 @@ void expand_to_path(struct index_state *istate,
 struct repository;
 int set_sparse_index_config(struct repository *repo, int enable);
 
+struct pattern_list;
+
+/**
+ * Scan the given index and compare its entries to the given pattern list.
+ * If the index is sparse and the pattern list uses cone mode patterns,
+ * then modify the index to contain the all of the file entries within that
+ * new pattern list. This expands sparse directories only as far as needed.
+ *
+ * If the pattern list is NULL or does not use cone mode patterns, then the
+ * index is expanded to a full index.
+ */
+void expand_index(struct index_state *istate, struct pattern_list *pl);
+
 #endif

gitgitgadget

From: Derrick Stolee <[email protected]>

A future change will present a temporary, in-memory mode where the index can both contain sparse directory entries but also not be completely collapsed to the smallest possible sparse directories. This will be necessary for modifying the sparse-checkout definition while using a sparse index.

For now, convert the single-bit member 'sparse_index' in 'struct index_state' to be a an 'enum sparse_index_mode' with three modes:

* INDEX_EXPANDED (0): No sparse directories exist. This is always the case for repositories that do not use cone-mode sparse-checkout.

* INDEX_COLLAPSED: Sparse directories may exist. Files outside the sparse-checkout cone are reduced to sparse directory entries whenever possible.

* INDEX_PARTIALLY_SPARSE: Sparse directories may exist. Some file entries outside the sparse-checkout cone may exist. Running convert_to_sparse() may further reduce those files to sparse directory entries.

The main reason to store this extra information is to allow convert_to_sparse() to short-circuit when the index is already in INDEX_EXPANDED mode but to actually do the necessary work when in INDEX_PARTIALLY_SPARSE mode.

The INDEX_PARTIALLY_SPARSE mode will be used in an upcoming change.

---
 builtin/sparse-checkout.c |  2 +-
 cache.h                   | 33 +++++++++++++++++++++++++--------
 read-cache.c              |  6 +++---
 sparse-index.c            |  6 +++---
 4 files changed, 32 insertions(+), 15 deletions(-)

index 0217d44c5b1..5b054400bf3 100644
@@ -128,7 +128,7 @@ static void clean_tracked_sparse_directories(struct repository *r)
 	 * sparse index will not delete directories that contain
 	 * conflicted entries or submodules.
 	 */
-	if (!r->index->sparse_index) {
+	if (r->index->sparse_index == INDEX_EXPANDED) {
 		/*
 		 * If something, such as a merge conflict or other concern,
 		 * prevents us from converting to a sparse index, then do

index 6226f6a8a53..e171ce882a2 100644
@@ -310,6 +310,29 @@ struct untracked_cache;
 struct progress;
 struct pattern_list;
 
+enum sparse_index_mode {
+	/*
+	 * There are no sparse directories in the index at all.
+	 *
+	 * Repositories that don't use cone-mode sparse-checkout will
+	 * always have their indexes in this mode.
+	 */
+	INDEX_EXPANDED = 0,
+
+	/*
+	 * The index has already been collapsed to sparse directories
+	 * whereever possible.
+	 */
+	INDEX_COLLAPSED,
+
+	/*
+	 * The sparse directories that exist are outside the
+	 * sparse-checkout boundary, but it is possible that some file
+	 * entries could collapse to sparse directory entries.
+	 */
+	INDEX_PARTIALLY_SPARSE,
+};
+
 struct index_state {
 	struct cache_entry **cache;
 	unsigned int version;

@@ -323,14 +346,8 @@ struct index_state {
 		 drop_cache_tree : 1,
 		 updated_workdir : 1,
 		 updated_skipworktree : 1,
-		 fsmonitor_has_run_once : 1,
-
-		 /*
-		  * sparse_index == 1 when sparse-directory
-		  * entries exist. Requires sparse-checkout
-		  * in cone mode.
-		  */
-		 sparse_index : 1;
+		 fsmonitor_has_run_once : 1;
+	enum sparse_index_mode sparse_index;
 	struct hashmap name_hash;
 	struct hashmap dir_hash;
 	struct object_id oid;

index 4df97e185e9..b236042eee1 100644
@@ -112,7 +112,7 @@ static const char *alternate_index_output;
 static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
 {
 	if (S_ISSPARSEDIR(ce->ce_mode))
-		istate->sparse_index = 1;
+		istate->sparse_index = INDEX_COLLAPSED;
 
 	istate->cache[nr] = ce;
 	add_name_hash(istate, ce);

@@ -1856,7 +1856,7 @@ static int read_index_extension(struct index_state *istate,
 		break;
 	case CACHE_EXT_SPARSE_DIRECTORIES:
 		/* no content, only an indicator */
-		istate->sparse_index = 1;
+		istate->sparse_index = INDEX_COLLAPSED;
 		break;
 	default:
 		if (*ext < 'A' || 'Z' < *ext)

@@ -3149,7 +3149,7 @@ static int do_write_locked_index(struct index_state *istate, struct lock_file *l
 				 unsigned flags)
 {
 	int ret;
-	int was_full = !istate->sparse_index;
+	int was_full = istate->sparse_index == INDEX_EXPANDED;
 
 	ret = convert_to_sparse(istate, 0);
 

index a11b5cf1314..7848910c154 100644
@@ -173,7 +173,7 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	 * If the index is already sparse, empty, or otherwise
 	 * cannot be converted to sparse, do not convert.
 	 */
-	if (istate->sparse_index || !istate->cache_nr ||
+	if (istate->sparse_index == INDEX_COLLAPSED || !istate->cache_nr ||
 	    !is_sparse_index_allowed(istate, flags))
 		return 0;
 

@@ -214,7 +214,7 @@ int convert_to_sparse(struct index_state *istate, int flags)
 	FREE_AND_NULL(istate->fsmonitor_dirty);
 	FREE_AND_NULL(istate->fsmonitor_last_update);
 
-	istate->sparse_index = 1;
+	istate->sparse_index = INDEX_COLLAPSED;
 	trace2_region_leave("index", "convert_to_sparse", istate->repo);
 	return 0;
 }

@@ -259,7 +259,7 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 	 * If the index is already full, then keep it full. We will convert
 	 * it to a sparse index on write, if possible.
 	 */
-	if (!istate || !istate->sparse_index)
+	if (!istate || istate->sparse_index == INDEX_EXPANDED)
 		return;
 
 	/*

gitgitgadget

From: Derrick Stolee <[email protected]>

Given a 'struct cache_tree', it may be beneficial to navigate directly to a node within that corresponds to a given path name. Create cache_tree_find_path() for this function. It returns NULL when no such path exists.

The implementation is adapted from do_invalidate_path() which does a similar search but also modifies the nodes it finds along the way. The method could be implemented simply using tail-recursion, but this while loop does the same thing.

This new method is not currently used, but will be in an upcoming change.

---
 cache-tree.c | 27 +++++++++++++++++++++++++++
 cache-tree.h |  2 ++
 2 files changed, 29 insertions(+)

index 6752f69d515..f42db920d10 100644
@@ -100,6 +100,33 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
 	return find_subtree(it, path, pathlen, 1);
 }
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path)
+{
+	const char *slash;
+	int namelen;
+	struct cache_tree_sub it_sub = {
+		.cache_tree = it,
+	};
+	struct cache_tree_sub *down = &it_sub;
+
+	while (down) {
+		slash = strchrnul(path, '/');
+		namelen = slash - path;
+		down->cache_tree->entry_count = -1;
+		if (!*slash) {
+			int pos;
+			pos = cache_tree_subtree_pos(down->cache_tree, path, namelen);
+			if (0 <= pos)
+				return down->cache_tree->down[pos]->cache_tree;
+			return NULL;
+		}
+		down = find_subtree(it, path, namelen, 0);
+		path = slash + 1;
+	}
+
+	return NULL;
+}
+
 static int do_invalidate_path(struct cache_tree *it, const char *path)
 {
 	/* a/b/c

index 8efeccebfc9..f75f8e74dcd 100644
@@ -29,6 +29,8 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *, const char *);
 
 int cache_tree_subtree_pos(struct cache_tree *it, const char *path, int pathlen);
 
+struct cache_tree *cache_tree_find_path(struct cache_tree *it, const char *path);
+
 void cache_tree_write(struct strbuf *, struct cache_tree *root);
 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size);
 

gitgitgadget

From: Derrick Stolee <[email protected]>

When the --no-sparse-index option is supplied, the sparse-checkout builtin should explicitly ask to expand a sparse index to a full one. This is currently done implicitly due to the command_requires_full_index protection, but that will be removed in an upcoming change.

---
 builtin/sparse-checkout.c | 3 +++
 1 file changed, 3 insertions(+)

index 5b054400bf3..1db51c3fd72 100644
@@ -413,6 +413,9 @@ static int update_modes(int *cone_mode, int *sparse_index)
 		/* force an index rewrite */
 		repo_read_index(the_repository);
 		the_repository->index->updated_workdir = 1;
+
+		if (!*sparse_index)
+			ensure_full_index(the_repository->index);
 	}
 
 	return 0;

gitgitgadget

From: Derrick Stolee <[email protected]>

The expand_to_pattern_list() method expands sparse directory entries to their list of contained files when either the pattern list is NULL or the directory is contained in the new pattern list's cone mode patterns.

It is possible that the pattern list has a recursive match with a directory 'A/B/C/' and so an existing sparse directory 'A/B/' would need to be expanded. If there exists a directory 'A/B/D/', then that directory should not be expanded and instead we can create a sparse directory.

To implement this, we plug into the add_path_to_index() callback for the call to read_tree_at(). Since we now need access to both the index we are writing and the pattern list we are comparing, create a 'struct modify_index_context' to use as a data transfer object. It is important that we use the given pattern list since we will use this pattern list to change the sparse-checkout patterns and cannot use istate->sparse_checkout_patterns.

---
 sparse-index.c | 57 +++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 50 insertions(+), 7 deletions(-)

index 7848910c154..a881f851810 100644
@@ -9,6 +9,11 @@
 #include "dir.h"
 #include "fsmonitor.h"
 
+struct modify_index_context {
+	struct index_state *write;
+	struct pattern_list *pl;
+};
+
 static struct cache_entry *construct_sparse_dir_entry(
 				struct index_state *istate,
 				const char *sparse_dir,

@@ -231,18 +236,52 @@ static int add_path_to_index(const struct object_id *oid,
 			     struct strbuf *base, const char *path,
 			     unsigned int mode, void *context)
 {
-	struct index_state *istate = (struct index_state *)context;
+	struct modify_index_context *ctx = (struct modify_index_context *)context;
 	struct cache_entry *ce;
 	size_t len = base->len;
 
-	if (S_ISDIR(mode))
-		return READ_TREE_RECURSIVE;
+	if (S_ISDIR(mode)) {
+		int dtype;
+		size_t baselen = base->len;
+		if (!ctx->pl)
+			return READ_TREE_RECURSIVE;
 
-	strbuf_addstr(base, path);
+		/*
+		 * Have we expanded to a point outside of the sparse-checkout?
+		 *
+		 * Artificially pad the path name with a slash "/" to
+		 * indicate it as a directory, and add an arbitrary file
+		 * name ("-") so we can consider base->buf as a file name
+		 * to match against the cone-mode patterns.
+		 *
+		 * If we compared just "path", then we would expand more
+		 * than we should. Since every file at root is always
+		 * included, we would expand every directory at root at
+		 * least one level deep instead of using sparse directory
+		 * entries.
+		 */
+		strbuf_addstr(base, path);
+		strbuf_add(base, "/-", 2);
+
+		if (path_matches_pattern_list(base->buf, base->len,
+					      NULL, &dtype,
+					      ctx->pl, ctx->write)) {
+			strbuf_setlen(base, baselen);
+			return READ_TREE_RECURSIVE;
+		}
 
-	ce = make_cache_entry(istate, mode, oid, base->buf, 0, 0);
+		/*
+		 * The path "{base}{path}/" is a sparse directory. Create the correct
+		 * name for inserting the entry into the index.
+		 */
+		strbuf_setlen(base, base->len - 1);
+	} else {
+		strbuf_addstr(base, path);
+	}
+
+	ce = make_cache_entry(ctx->write, mode, oid, base->buf, 0, 0);
 	ce->ce_flags |= CE_SKIP_WORKTREE | CE_EXTENDED;
-	set_index_entry(istate, istate->cache_nr++, ce);
+	set_index_entry(ctx->write, ctx->write->cache_nr++, ce);
 
 	strbuf_setlen(base, len);
 	return 0;

@@ -254,6 +293,7 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 	struct index_state *full;
 	struct strbuf base = STRBUF_INIT;
 	const char *tr_region;
+	struct modify_index_context ctx;
 
 	/*
 	 * If the index is already full, then keep it full. We will convert

@@ -293,6 +333,9 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 	full->cache_nr = 0;
 	ALLOC_ARRAY(full->cache, full->cache_alloc);
 
+	ctx.write = full;
+	ctx.pl = pl;
+
 	for (i = 0; i < istate->cache_nr; i++) {
 		struct cache_entry *ce = istate->cache[i];
 		struct tree *tree;

@@ -318,7 +361,7 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 		strbuf_add(&base, ce->name, strlen(ce->name));
 
 		read_tree_at(istate->repo, tree, &base, &ps,
-			     add_path_to_index, full);
+			     add_path_to_index, &ctx);
 
 		/* free directory entries. full entries are re-used */
 		discard_cache_entry(ce);

gitgitgadget

From: Derrick Stolee <[email protected]>

To complete the implementation of expand_to_pattern_list(), we need to detect when a sparse directory entry should remain sparse. This avoids a full expansion, so we now need to use the PARTIALLY_SPARSE mode to indicate this state.

There still are no callers to this method, but we will add one in the next change.

---
 sparse-index.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

index a881f851810..2c0a18380f1 100644
@@ -308,8 +308,24 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 	 * continue. A NULL pattern set indicates a full expansion to a
 	 * full index.
 	 */
-	if (pl && !pl->use_cone_patterns)
+	if (pl && !pl->use_cone_patterns) {
 		pl = NULL;
+	} else {
+		/*
+		 * We might contract file entries into sparse-directory
+		 * entries, and for that we will need the cache tree to
+		 * be recomputed.
+		 */
+		cache_tree_free(&istate->cache_tree);
+
+		/*
+		 * If there is a problem creating the cache tree, then we
+		 * need to expand to a full index since we cannot satisfy
+		 * the current request as a sparse index.
+		 */
+		if (cache_tree_update(istate, 0))
+			pl = NULL;
+	}
 
 	if (!istate->repo)
 		istate->repo = the_repository;

@@ -327,8 +343,14 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 	full = xcalloc(1, sizeof(struct index_state));
 	memcpy(full, istate, sizeof(struct index_state));
 
+	/*
+	 * This slightly-misnamed 'full' index might still be sparse if we
+	 * are only modifying the list of sparse directories. This hinges
+	 * on whether we have a non-NULL pattern list.
+	 */
+	full->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;
+
 	/* then change the necessary things */
-	full->sparse_index = 0;
 	full->cache_alloc = (3 * istate->cache_alloc) / 2;
 	full->cache_nr = 0;
 	ALLOC_ARRAY(full->cache, full->cache_alloc);

@@ -340,11 +362,22 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 		struct cache_entry *ce = istate->cache[i];
 		struct tree *tree;
 		struct pathspec ps;
+		int dtype;
 
 		if (!S_ISSPARSEDIR(ce->ce_mode)) {
 			set_index_entry(full, full->cache_nr++, ce);
 			continue;
 		}
+
+		/* We now have a sparse directory entry. Should we expand? */
+		if (pl &&
+		    path_matches_pattern_list(ce->name, ce->ce_namelen,
+					      NULL, &dtype,
+					      pl, istate) == NOT_MATCHED) {
+			set_index_entry(full, full->cache_nr++, ce);
+			continue;
+		}
+
 		if (!(ce->ce_flags & CE_SKIP_WORKTREE))
 			warning(_("index entry is a directory, but not sparse (%08x)"),
 				ce->ce_flags);

@@ -370,7 +403,7 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 	/* Copy back into original index. */
 	memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
 	memcpy(&istate->dir_hash, &full->dir_hash, sizeof(full->dir_hash));
-	istate->sparse_index = 0;
+	istate->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;
 	free(istate->cache);
 	istate->cache = full->cache;
 	istate->cache_nr = full->cache_nr;

gitgitgadget

From: Derrick Stolee <[email protected]>

The sparse-checkout builtin is almost completely integrated with the sparse index, allowing the sparse-checkout boundary to be modified without expanding a sparse index to a full one. Add a test to p2000-sparse-operations.sh that adds a directory to the sparse-checkout definition, then removes it. Using both operations is important to ensure that the operation is doing the same work in each repetition as well as leaving the test repo in a good state for later tests.