ls-files: conditionally leave index sparse

From: Derrick Stolee <[email protected]>

Replace this global check to expand the index with a check inside the loop for a matched sparse directory. If we see one, then expand the index and continue from the current location. This is safe since the previous entries in the index did not have any sparse directories and thus would remain stable in this expansion.

Quoted 1 line · Derrick Stolee via GitGitGadget

From: Derrick Stolee <[email protected]>

...

Quoted 5 lines

Replace this global check to expand the index with a check inside the loop for a matched sparse directory. If we see one, then expand the index and continue from the current location. This is safe since the previous entries in the index did not have any sparse directories and thus would remain stable in this expansion.

...> Here's a small sparse index performance update based on a user report.

I know this is small and somewhat niche, but it hasn't had any review or been picked up in What's Cooking. Could someone please take a look?

Quoted 10 lines · Derrick Stolee

Quoted 1 line · Derrick Stolee via GitGitGadget

From: Derrick Stolee <[email protected]>

...

Quoted 5 lines

Replace this global check to expand the index with a check inside the loop for a matched sparse directory. If we see one, then expand the index and continue from the current location. This is safe since the previous entries in the index did not have any sparse directories and thus would remain stable in this expansion.

...> Here's a small sparse index performance update based on a user report.

Quoted 2 lines

I know this is small and somewhat niche, but it hasn't had any review or been picked up in What's Cooking. Could someone please take a look?

Thanks, Elijah and Junio for reviewing.

By coincidence, a user reported an issue where the sparse index was expanded during "git mergetool" and it was due to a pathspec-focused ls-files subcommand. So maybe it's less niche than I had thought.

From: Derrick Stolee <[email protected]>

When running 'git ls-files' with a pathspec, the index entries get filtered according to that pathspec before iterating over them in

show_files(). In 78087097b8 (ls-files: add --sparse option, 2021-12-22), this iteration was prefixed with a check for the '--sparse' option which allows the command to output directory entries; this created a pre-loop call to ensure_full_index().

However, when a user runs 'git ls-files' where the pathspec matches directories that are recursively matched in the sparse-checkout, there are not any sparse directories that match the pathspec so they would not be written to the output. The expansion in this case is just a performance drop for no behavior difference.

Replace this global check to expand the index with a check inside the loop for a matched sparse directory. If we see one, then expand the index and continue from the current location. This is safe since the previous entries in the index did not have any sparse directories and thus would remain stable in this expansion.

A test in t1092 confirms that this changes the behavior.

Signed-off-by Derrick Stolee <[email protected]>

---
ls-files: conditionally leave index sparse

Here's a small sparse index performance update based on a user report.

Thanks, -Stolee

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1955%2Fderrickstolee%2Fls-files-sparse-index-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1955/derrickstolee/ls-files-sparse-index-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1955

 builtin/ls-files.c                       | 13 ++++++++++---
 t/t1092-sparse-checkout-compatibility.sh | 13 +++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

builtin/ls-files.c +0 -3

index c06a6f33e41..b148607f7a1 100644
@@ -414,14 +414,21 @@ static void show_files(struct repository *repo, struct dir_struct *dir)
        if (!(show_cached || show_stage || show_deleted || show_modified))
                return;
 
-       if (!show_sparse_dirs)
-               ensure_full_index(repo->index);
-
        for (i = 0; i < repo->index->cache_nr; i++) {
                const struct cache_entry *ce = repo->index->cache[i];
                struct stat st;
                int stat_err;

t/t1092-sparse-checkout-compatibility.sh +1 -0

        echo >>sparse-index/README.md &&
        ensure_not_expanded add -A &&
        echo >>sparse-index/extra.txt &&

@@ -1607,6 +1609,17 @@ test_expect_success 'describe tested on all' '
        test_all_match git describe --dirty
 '
 
+test_expect_success 'ls-files filtering and expansion' '