Allow passing pathspecs to git range-diff

I just had the need to find out upstream commits corresponding to a handful of backported commits, and most importantly, identify upstream commits touching a given file that had not yet been backported.

This new mode helped me identify them.

Johannes Schindelin (2):
range-diff: reorder argument handling
range-diff: optionally accept a pathspec

 Documentation/git-range-diff.txt |  4 +++
 builtin/range-diff.c             | 54 ++++++++++++++++++++++++--------
 range-diff.c                     |  2 +-
 t/t3206-range-diff.sh            | 11 +++++++
 4 files changed, 57 insertions(+), 14 deletions(-)

base-commit: 795ea8776befc95ea2becd8020c7a284677b4161
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1335%2Fdscho%2Frange-diff-with-pathspec-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1335/dscho/range-diff-with-pathspec-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1335

gitgitgadget

From: Johannes Schindelin <[email protected]>

In d9c66f0b5bf (range-diff: first rudimentary implementation, 2018-08-13), we introduced the argument handling of the range-diff command, special-casing three different stanzas based on the argument count.

The somewhat unorthodox order (first handling the case of 2 arguments, then 3, then 1) was chosen for clarity: the natural argument number is 2 because that is how many revision ranges are used internally. The code to handle three arguments is relatively trivial, so it was added next. And finally, the code to ungarble a single symmetric range into two separate ones was added, because it was the most complicated (the most inelegant part being about interpreting empty sides of the symmetric range as HEAD).

In preparation for allowing pathspecs in git range-diff invocations, where we no longer have the luxury of using the number of arguments to disambiguate between these three different ways to specify the commit ranges, we need to order these cases by argument count, in ascending order.

This patch is best viewed with --color-moved.

---
 builtin/range-diff.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

index 50318849d65..c8ffcd35aea 100644
@@ -55,18 +55,7 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 	if (!simple_color)
 		diffopt.use_color = 1;
 
-	if (argc == 2) {
-		if (!is_range_diff_range(argv[0]))
-			die(_("not a commit range: '%s'"), argv[0]);
-		strbuf_addstr(&range1, argv[0]);
-
-		if (!is_range_diff_range(argv[1]))
-			die(_("not a commit range: '%s'"), argv[1]);
-		strbuf_addstr(&range2, argv[1]);
-	} else if (argc == 3) {
-		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
-		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
-	} else if (argc == 1) {
+	if (argc == 1) {
 		const char *b = strstr(argv[0], "..."), *a = argv[0];
 		int a_len;
 

@@ -85,6 +74,17 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 			b = "HEAD";
 		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
 		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
+	} else if (argc == 2) {
+		if (!is_range_diff_range(argv[0]))
+			die(_("not a commit range: '%s'"), argv[0]);
+		strbuf_addstr(&range1, argv[0]);
+
+		if (!is_range_diff_range(argv[1]))
+			die(_("not a commit range: '%s'"), argv[1]);
+		strbuf_addstr(&range2, argv[1]);
+	} else if (argc == 3) {
+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
 	} else {
 		error(_("need two commit ranges"));
 		usage_with_options(builtin_range_diff_usage, options);

gitgitgadget

From: Johannes Schindelin <[email protected]>

The git range-diff command can be quite expensive, which is not a surprise given that the underlying algorithm to match up pairs of commits between the provided two commit ranges has a cubic runtime.

Therefore it makes sense to restrict the commit ranges as much as possible, to reduce the amount of input to that O(N^3) algorithm.

In chatty repositories with wide trees, this is not necessarily possible merely by choosing commit ranges wisely.

Let's give users another option to restrict the commit ranges: by providing a pathspec. That helps in repositories with wide trees because it is likely that the user has a good idea which subset of the tree they are actually interested in.

Example:

git range-diff upstream/main upstream/seen HEAD -- range-diff.c

This shows commits that are either in the local branch or in seen, but not in main, skipping all commits that do not touch range-diff.c.

Note: Since we piggy-back the pathspecs onto the other_arg mechanism that was introduced to be able to pass through the --notes option to the revision machinery, we must now ensure that the other_arg array is appended at the end (the revision range must come before the pathspecs, if any).

---
 Documentation/git-range-diff.txt |  4 ++++
 builtin/range-diff.c             | 30 +++++++++++++++++++++++++++++-
 range-diff.c                     |  2 +-
 t/t3206-range-diff.sh            | 11 +++++++++++
 4 files changed, 45 insertions(+), 2 deletions(-)

index fe350d7f405..0b393715d70 100644
@@ -12,6 +12,7 @@ SYNOPSIS
 	[--no-dual-color] [--creation-factor=<factor>]
 	[--left-only | --right-only]
 	( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> )
+	[[--] <path>...]
 
 DESCRIPTION
 -----------

@@ -19,6 +20,9 @@ DESCRIPTION
 This command shows the differences between two versions of a patch
 series, or more generally, two commit ranges (ignoring merge commits).
 
+In the presence of `<path>` arguments, these commit ranges are limited
+accordingly.
+
 To that end, it first finds pairs of commits from both commit ranges
 that correspond with each other. Two commits are said to correspond when
 the diff between their patches (i.e. the author information, the commit

index c8ffcd35aea..9ae95b9c950 100644
@@ -40,6 +40,8 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 	struct option *options;
 	int res = 0;
 	struct strbuf range1 = STRBUF_INIT, range2 = STRBUF_INIT;
+	struct object_id oid;
+	const char *p;
 
 	git_config(git_diff_ui_config, NULL);
 

@@ -47,7 +49,7 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 
 	options = parse_options_concat(range_diff_options, diffopt.parseopts);
 	argc = parse_options(argc, argv, prefix, options,
-			     builtin_range_diff_usage, 0);
+			     builtin_range_diff_usage, PARSE_OPT_KEEP_DASHDASH);
 
 	diff_setup_done(&diffopt);
 

@@ -74,6 +76,20 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 			b = "HEAD";
 		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
 		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
+	} else if (argc > 1 && (p = strstr(argv[0], "..."))) {
+		const char *a = argv[0];
+		int a_len = (int)(p - a);
+
+		if (!a_len) {
+			a = "HEAD";
+			a_len = strlen(a);
+		}
+		p += 3;
+		if (!*p)
+			p = "HEAD";
+		strbuf_addf(&range1, "%s..%.*s", p, a_len, a);
+		strbuf_addf(&range2, "%.*s..%s", a_len, a, p);
+		strvec_pushv(&other_arg, argv + 1);
 	} else if (argc == 2) {
 		if (!is_range_diff_range(argv[0]))
 			die(_("not a commit range: '%s'"), argv[0]);

@@ -82,9 +98,21 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 		if (!is_range_diff_range(argv[1]))
 			die(_("not a commit range: '%s'"), argv[1]);
 		strbuf_addstr(&range2, argv[1]);
+	} else if (argc > 2 &&
+	    is_range_diff_range(argv[0]) && is_range_diff_range(argv[1])) {
+		strbuf_addstr(&range1, argv[0]);
+		strbuf_addstr(&range2, argv[1]);
+		strvec_pushv(&other_arg, argv + 2);
 	} else if (argc == 3) {
 		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
 		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
+	} else if (argc > 3 &&
+		   get_oid_committish(argv[0], &oid) &&
+		   get_oid_committish(argv[1], &oid) &&
+		   get_oid_committish(argv[2], &oid)) {
+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
+		strvec_pushv(&other_arg, argv + 3);
 	} else {
 		error(_("need two commit ranges"));
 		usage_with_options(builtin_range_diff_usage, options);

index f63b3ffc200..124dd678c38 100644
@@ -57,9 +57,9 @@ static int read_patches(const char *range, struct string_list *list,
 		     "--pretty=medium",
 		     "--notes",
 		     NULL);
+	strvec_push(&cp.args, range);
 	if (other_arg)
 		strvec_pushv(&cp.args, other_arg->v);
-	strvec_push(&cp.args, range);
 	cp.out = -1;
 	cp.no_stdin = 1;
 	cp.git_cmd = 1;

index d12e4e4cc6c..f2821a69b6f 100755
@@ -772,6 +772,17 @@ test_expect_success '--left-only/--right-only' '
 	test_cmp expect actual
 '
 
+test_expect_success 'ranges with pathspecs' '
+	git range-diff topic...mode-only-change -- other-file >actual &&
+	test_line_count = 2 actual &&
+	topic_oid=$(git rev-parse --short topic) &&
+	mode_change_oid=$(git rev-parse --short mode-only-change^) &&
+	file_change_oid=$(git rev-parse --short mode-only-change) &&
+	grep "$mode_change_oid" actual &&
+	! grep "$file_change_oid" actual &&
+	! grep "$topic_oid" actual
+'
+
 test_expect_success 'submodule changes are shown irrespective of diff.submodule' '
 	git init sub-repo &&
 	test_commit -C sub-repo sub-first &&

gitgitgadget

"Johannes Schindelin via GitGitGadget" <[email protected]>

It is excellent that this now takes pathspec to sparsify the history.

The implementation looks, eh, a bit dirty with obvious repetitions in the "..." case and two-ranges cases. Three-arg cases sort-of looks different but that is because the original one does not even bother to ensure argv[0] and argv[1] are objects, while the new one does, so they are essentially doing the same things.

I just had the need to find out upstream commits corresponding to a handful of backported commits, and most importantly, identify upstream commits touching a given file that had not yet been backported.

This new mode helped me identify them.

Changes since v1:

* The command-line parameter parsing now avoids duplicating code as much as possible.
* This also fixes a bug where git range-diff <incorrect-symmetric-range> -- <pathspec> was mistaken for using the three-revision stanza.
* Consistent validation of the command-line arguments has been extracted into its own patch.
* Sadly, these changes make the overall diff much larger. I hope that the readability is worth that price.

Johannes Schindelin (3):
range-diff: reorder argument handling
range-diff: consistently validate the arguments
range-diff: optionally accept pathspecs

 Documentation/git-range-diff.txt |   4 ++
 builtin/range-diff.c             | 101 +++++++++++++++++++++++--------
 range-diff.c                     |   2 +-
 t/t3206-range-diff.sh            |  13 +++-
 4 files changed, 94 insertions(+), 26 deletions(-)

base-commit: 795ea8776befc95ea2becd8020c7a284677b4161
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1335%2Fdscho%2Frange-diff-with-pathspec-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1335/dscho/range-diff-with-pathspec-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1335

Range-diff vs v1:

1: 7fe4f228ae0 ! 1: 150f29a1c48 range-diff: reorder argument handling

     @@ Commit message
          In preparation for allowing pathspecs in `git range-diff` invocations,
          where we no longer have the luxury of using the number of arguments to
          disambiguate between these three different ways to specify the commit
     -    ranges, we need to order these cases by argument count, in ascending
     +    ranges, we need to order these cases by argument count, in descending
          order.
      
          This patch is best viewed with `--color-moved`.
     @@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char
       		diffopt.use_color = 1;
       
      -	if (argc == 2) {
     --		if (!is_range_diff_range(argv[0]))
     --			die(_("not a commit range: '%s'"), argv[0]);
     --		strbuf_addstr(&range1, argv[0]);
     --
     --		if (!is_range_diff_range(argv[1]))
     --			die(_("not a commit range: '%s'"), argv[1]);
     --		strbuf_addstr(&range2, argv[1]);
     ++	if (argc == 3) {
     ++		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
     ++		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
     ++	} else if (argc == 2) {
     + 		if (!is_range_diff_range(argv[0]))
     + 			die(_("not a commit range: '%s'"), argv[0]);
     + 		strbuf_addstr(&range1, argv[0]);
     +@@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char *prefix)
     + 		if (!is_range_diff_range(argv[1]))
     + 			die(_("not a commit range: '%s'"), argv[1]);
     + 		strbuf_addstr(&range2, argv[1]);
      -	} else if (argc == 3) {
      -		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
      -		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
     --	} else if (argc == 1) {
     -+	if (argc == 1) {
     + 	} else if (argc == 1) {
       		const char *b = strstr(argv[0], "..."), *a = argv[0];
       		int a_len;
     - 
     -@@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char *prefix)
     - 			b = "HEAD";
     - 		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
     - 		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
     -+	} else if (argc == 2) {
     -+		if (!is_range_diff_range(argv[0]))
     -+			die(_("not a commit range: '%s'"), argv[0]);
     -+		strbuf_addstr(&range1, argv[0]);
     -+
     -+		if (!is_range_diff_range(argv[1]))
     -+			die(_("not a commit range: '%s'"), argv[1]);
     -+		strbuf_addstr(&range2, argv[1]);
     -+	} else if (argc == 3) {
     -+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
     -+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
     - 	} else {
     - 		error(_("need two commit ranges"));
     - 		usage_with_options(builtin_range_diff_usage, options);
 -:  ----------- > 2:  4cd7f09557c range-diff: consistently validate the arguments
 2:  064b147451b ! 3:  a52ad40e015 range-diff: optionally accept a pathspec
     @@ Metadata
      Author: Johannes Schindelin <[email protected]>
      
       ## Commit message ##
     -    range-diff: optionally accept a pathspec
     +    range-diff: optionally accept pathspecs
      
          The `git range-diff` command can be quite expensive, which is not a
          surprise given that the underlying algorithm to match up pairs of
     @@ Documentation/git-range-diff.txt: DESCRIPTION
      
       ## builtin/range-diff.c ##
      @@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char *prefix)
     + 		OPT_END()
     + 	};
       	struct option *options;
     - 	int res = 0;
     +-	int res = 0;
     ++	int i, dash_dash = -1, res = 0;
       	struct strbuf range1 = STRBUF_INIT, range2 = STRBUF_INIT;
     -+	struct object_id oid;
     -+	const char *p;
     + 	struct object_id oid;
     ++	const char *three_dots = NULL;
       
       	git_config(git_diff_ui_config, NULL);
       
     @@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char
       	diff_setup_done(&diffopt);
       
      @@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char *prefix)
     - 			b = "HEAD";
     - 		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
     - 		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
     -+	} else if (argc > 1 && (p = strstr(argv[0], "..."))) {
     -+		const char *a = argv[0];
     -+		int a_len = (int)(p - a);
     -+
     -+		if (!a_len) {
     -+			a = "HEAD";
     -+			a_len = strlen(a);
     + 	if (!simple_color)
     + 		diffopt.use_color = 1;
     + 
     +-	if (argc == 3) {
     +-		if (get_oid_committish(argv[0], &oid))
     ++	for (i = 0; i < argc; i++)
     ++		if (!strcmp(argv[i], "--")) {
     ++			dash_dash = i;
     ++			break;
      +		}
     -+		p += 3;
     -+		if (!*p)
     -+			p = "HEAD";
     -+		strbuf_addf(&range1, "%s..%.*s", p, a_len, a);
     -+		strbuf_addf(&range2, "%.*s..%s", a_len, a, p);
     -+		strvec_pushv(&other_arg, argv + 1);
     - 	} else if (argc == 2) {
     - 		if (!is_range_diff_range(argv[0]))
     - 			die(_("not a commit range: '%s'"), argv[0]);
     ++
     ++	if (dash_dash == 3 ||
     ++	    (dash_dash < 0 && argc > 2 &&
     ++	     !get_oid_committish(argv[0], &oid) &&
     ++	     !get_oid_committish(argv[1], &oid) &&
     ++	     !get_oid_committish(argv[2], &oid))) {
     ++		if (dash_dash < 0)
     ++			; /* already validated arguments */
     ++		else if (get_oid_committish(argv[0], &oid))
     + 			usage_msg_optf(_("not a revision: '%s'"),
     + 				       builtin_range_diff_usage, options,
     + 				       argv[0]);
      @@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char *prefix)
     - 		if (!is_range_diff_range(argv[1]))
     - 			die(_("not a commit range: '%s'"), argv[1]);
     - 		strbuf_addstr(&range2, argv[1]);
     -+	} else if (argc > 2 &&
     -+	    is_range_diff_range(argv[0]) && is_range_diff_range(argv[1])) {
     -+		strbuf_addstr(&range1, argv[0]);
     -+		strbuf_addstr(&range2, argv[1]);
     -+		strvec_pushv(&other_arg, argv + 2);
     - 	} else if (argc == 3) {
     + 
       		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
       		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
     -+	} else if (argc > 3 &&
     -+		   get_oid_committish(argv[0], &oid) &&
     -+		   get_oid_committish(argv[1], &oid) &&
     -+		   get_oid_committish(argv[2], &oid)) {
     -+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
     -+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
     -+		strvec_pushv(&other_arg, argv + 3);
     - 	} else {
     - 		error(_("need two commit ranges"));
     - 		usage_with_options(builtin_range_diff_usage, options);
     +-	} else if (argc == 2) {
     +-		if (!is_range_diff_range(argv[0]))
     ++
     ++		strvec_pushv(&other_arg, argv +
     ++			     (dash_dash < 0 ? 3 : dash_dash));
     ++	} else if (dash_dash == 2 ||
     ++		   (dash_dash < 0 && argc > 1 &&
     ++		    is_range_diff_range(argv[0]) &&
     ++		    is_range_diff_range(argv[1]))) {
     ++		if (dash_dash < 0)
     ++			; /* already validated arguments */
     ++		else if (!is_range_diff_range(argv[0]))
     + 			usage_msg_optf(_("not a commit range: '%s'"),
     + 				       builtin_range_diff_usage, options,
     + 				       argv[0]);
     +@@ builtin/range-diff.c: int cmd_range_diff(int argc, const char **argv, const char *prefix)
     + 
     + 		strbuf_addstr(&range1, argv[0]);
     + 		strbuf_addstr(&range2, argv[1]);
     +-	} else if (argc == 1) {
     +-		const char *b = strstr(argv[0], "..."), *a = argv[0];
     ++
     ++		strvec_pushv(&other_arg, argv +
     ++			     (dash_dash < 0 ? 2 : dash_dash));
     ++	} else if (dash_dash == 1 ||
     ++		   (dash_dash < 0 && argc > 0 &&
     ++		    (three_dots = strstr(argv[0], "...")))) {
     ++		const char *a, *b;
     + 		int a_len;
     + 
     +-		if (!b)
     ++		if (dash_dash < 0)
     ++			; /* already validated arguments */
     ++		else if (!(three_dots = strstr(argv[0], "...")))
     + 			usage_msg_optf(_("not a symmetric range: '%s'"),
     +-				       builtin_range_diff_usage, options,
     +-				       argv[0]);
     ++					 builtin_range_diff_usage, options,
     ++					 argv[0]);
     + 
     +-		a_len = (int)(b - a);
     +-		if (!a_len) {
     ++		if (three_dots == argv[0]) {
     + 			a = "HEAD";
     + 			a_len = strlen(a);
     ++		} else {
     ++			a = argv[0];
     ++			a_len = (int)(three_dots - a);
     + 		}
     +-		b += 3;
     +-		if (!*b)
     ++
     ++		if (three_dots[3])
     ++			b = three_dots + 3;
     ++		else
     + 			b = "HEAD";
     ++
     + 		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
     + 		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
     ++
     ++		strvec_pushv(&other_arg, argv +
     ++			     (dash_dash < 0 ? 1 : dash_dash));
     + 	} else
     + 		usage_msg_opt(_("need two commit ranges"),
     + 			      builtin_range_diff_usage, options);
      
       ## range-diff.c ##
      @@ range-diff.c: static int read_patches(const char *range, struct string_list *list,
     @@ range-diff.c: static int read_patches(const char *range, struct string_list *lis
       	cp.git_cmd = 1;
      
       ## t/t3206-range-diff.sh ##
     +@@ t/t3206-range-diff.sh: test_expect_success 'A^! and A^-<n> (unmodified)' '
     + '
     + 
     + test_expect_success 'A^{/..} is not mistaken for a range' '
     +-	test_must_fail git range-diff topic^.. topic^{/..} 2>error &&
     ++	test_must_fail git range-diff topic^.. topic^{/..} -- 2>error &&
     + 	test_i18ngrep "not a commit range" error
     + '
     + 
      @@ t/t3206-range-diff.sh: test_expect_success '--left-only/--right-only' '
       	test_cmp expect actual
       '

gitgitgadget

From: Johannes Schindelin <[email protected]>

In d9c66f0b5bf (range-diff: first rudimentary implementation, 2018-08-13), we introduced the argument handling of the range-diff command, special-casing three different stanzas based on the argument count.

The somewhat unorthodox order (first handling the case of 2 arguments, then 3, then 1) was chosen for clarity: the natural argument number is 2 because that is how many revision ranges are used internally. The code to handle three arguments is relatively trivial, so it was added next. And finally, the code to ungarble a single symmetric range into two separate ones was added, because it was the most complicated (the most inelegant part being about interpreting empty sides of the symmetric range as HEAD).

In preparation for allowing pathspecs in git range-diff invocations, where we no longer have the luxury of using the number of arguments to disambiguate between these three different ways to specify the commit ranges, we need to order these cases by argument count, in descending order.

This patch is best viewed with --color-moved.

---
 builtin/range-diff.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

index 50318849d65..f8d3869d357 100644
@@ -55,7 +55,10 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 	if (!simple_color)
 		diffopt.use_color = 1;
 
-	if (argc == 2) {
+	if (argc == 3) {
+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
+	} else if (argc == 2) {
 		if (!is_range_diff_range(argv[0]))
 			die(_("not a commit range: '%s'"), argv[0]);
 		strbuf_addstr(&range1, argv[0]);

@@ -63,9 +66,6 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 		if (!is_range_diff_range(argv[1]))
 			die(_("not a commit range: '%s'"), argv[1]);
 		strbuf_addstr(&range2, argv[1]);
-	} else if (argc == 3) {
-		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
-		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
 	} else if (argc == 1) {
 		const char *b = strstr(argv[0], "..."), *a = argv[0];
 		int a_len;

gitgitgadget

From: Johannes Schindelin <[email protected]>

This patch lets range-diff validate the arguments not only when invoked with one or two arguments, but also in the code path where three arguments are handled.

While at it, we now use usage_msg_opt*() consistently.

---
 builtin/range-diff.c | 41 +++++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

index f8d3869d357..71319ed1d84 100644
@@ -40,6 +40,7 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 	struct option *options;
 	int res = 0;
 	struct strbuf range1 = STRBUF_INIT, range2 = STRBUF_INIT;
+	struct object_id oid;
 
 	git_config(git_diff_ui_config, NULL);
 

@@ -56,24 +57,41 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 		diffopt.use_color = 1;
 
 	if (argc == 3) {
+		if (get_oid_committish(argv[0], &oid))
+			usage_msg_optf(_("not a revision: '%s'"),
+				       builtin_range_diff_usage, options,
+				       argv[0]);
+		else if (get_oid_committish(argv[1], &oid))
+			usage_msg_optf(_("not a revision: '%s'"),
+				       builtin_range_diff_usage, options,
+				       argv[1]);
+		else if (get_oid_committish(argv[2], &oid))
+			usage_msg_optf(_("not a revision: '%s'"),
+				       builtin_range_diff_usage, options,
+				       argv[2]);
+
 		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
 		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
 	} else if (argc == 2) {
 		if (!is_range_diff_range(argv[0]))
-			die(_("not a commit range: '%s'"), argv[0]);
-		strbuf_addstr(&range1, argv[0]);
+			usage_msg_optf(_("not a commit range: '%s'"),
+				       builtin_range_diff_usage, options,
+				       argv[0]);
+		else if (!is_range_diff_range(argv[1]))
+			usage_msg_optf(_("not a commit range: '%s'"),
+				       builtin_range_diff_usage, options,
+				       argv[1]);
 
-		if (!is_range_diff_range(argv[1]))
-			die(_("not a commit range: '%s'"), argv[1]);
+		strbuf_addstr(&range1, argv[0]);
 		strbuf_addstr(&range2, argv[1]);
 	} else if (argc == 1) {
 		const char *b = strstr(argv[0], "..."), *a = argv[0];
 		int a_len;
 
-		if (!b) {
-			error(_("single arg format must be symmetric range"));
-			usage_with_options(builtin_range_diff_usage, options);
-		}
+		if (!b)
+			usage_msg_optf(_("not a symmetric range: '%s'"),
+				       builtin_range_diff_usage, options,
+				       argv[0]);
 
 		a_len = (int)(b - a);
 		if (!a_len) {

@@ -85,10 +103,9 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 			b = "HEAD";
 		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
 		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
-	} else {
-		error(_("need two commit ranges"));
-		usage_with_options(builtin_range_diff_usage, options);
-	}
+	} else
+		usage_msg_opt(_("need two commit ranges"),
+			      builtin_range_diff_usage, options);
 	FREE_AND_NULL(options);
 
 	range_diff_opts.dual_color = simple_color < 1;

gitgitgadget

"Johannes Schindelin via GitGitGadget" <[email protected]>

Very nice. The updated series is worth having if only for this step. Very very pleasing.

From: Johannes Schindelin <[email protected]>

The git range-diff command can be quite expensive, which is not a surprise given that the underlying algorithm to match up pairs of commits between the provided two commit ranges has a cubic runtime.

Therefore it makes sense to restrict the commit ranges as much as possible, to reduce the amount of input to that O(N^3) algorithm.

In chatty repositories with wide trees, this is not necessarily possible merely by choosing commit ranges wisely.

Let's give users another option to restrict the commit ranges: by providing a pathspec. That helps in repositories with wide trees because it is likely that the user has a good idea which subset of the tree they are actually interested in.

Example:

git range-diff upstream/main upstream/seen HEAD -- range-diff.c

This shows commits that are either in the local branch or in seen, but not in main, skipping all commits that do not touch range-diff.c.

Note: Since we piggy-back the pathspecs onto the other_arg mechanism that was introduced to be able to pass through the --notes option to the revision machinery, we must now ensure that the other_arg array is appended at the end (the revision range must come before the pathspecs, if any).

---
 Documentation/git-range-diff.txt |  4 ++
 builtin/range-diff.c             | 66 ++++++++++++++++++++++++--------
 range-diff.c                     |  2 +-
 t/t3206-range-diff.sh            | 13 ++++++-
 4 files changed, 68 insertions(+), 17 deletions(-)

index fe350d7f405..0b393715d70 100644
@@ -12,6 +12,7 @@ SYNOPSIS
 	[--no-dual-color] [--creation-factor=<factor>]
 	[--left-only | --right-only]
 	( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> )
+	[[--] <path>...]
 
 DESCRIPTION
 -----------

@@ -19,6 +20,9 @@ DESCRIPTION
 This command shows the differences between two versions of a patch
 series, or more generally, two commit ranges (ignoring merge commits).
 
+In the presence of `<path>` arguments, these commit ranges are limited
+accordingly.
+
 To that end, it first finds pairs of commits from both commit ranges
 that correspond with each other. Two commits are said to correspond when
 the diff between their patches (i.e. the author information, the commit

index f63b3ffc200..124dd678c38 100644
@@ -57,9 +57,9 @@ static int read_patches(const char *range, struct string_list *list,
 		     "--pretty=medium",
 		     "--notes",
 		     NULL);
+	strvec_push(&cp.args, range);
 	if (other_arg)
 		strvec_pushv(&cp.args, other_arg->v);
-	strvec_push(&cp.args, range);
 	cp.out = -1;
 	cp.no_stdin = 1;
 	cp.git_cmd = 1;

index d12e4e4cc6c..459beaf7d9c 100755
@@ -162,7 +162,7 @@ test_expect_success 'A^! and A^-<n> (unmodified)' '
 '
 
 test_expect_success 'A^{/..} is not mistaken for a range' '
-	test_must_fail git range-diff topic^.. topic^{/..} 2>error &&
+	test_must_fail git range-diff topic^.. topic^{/..} -- 2>error &&
 	test_i18ngrep "not a commit range" error
 '
 

@@ -772,6 +772,17 @@ test_expect_success '--left-only/--right-only' '
 	test_cmp expect actual
 '
 
+test_expect_success 'ranges with pathspecs' '
+	git range-diff topic...mode-only-change -- other-file >actual &&
+	test_line_count = 2 actual &&
+	topic_oid=$(git rev-parse --short topic) &&
+	mode_change_oid=$(git rev-parse --short mode-only-change^) &&
+	file_change_oid=$(git rev-parse --short mode-only-change) &&
+	grep "$mode_change_oid" actual &&
+	! grep "$file_change_oid" actual &&
+	! grep "$topic_oid" actual
+'
+
 test_expect_success 'submodule changes are shown irrespective of diff.submodule' '
 	git init sub-repo &&
 	test_commit -C sub-repo sub-first &&

gitgitgadget

"Johannes Schindelin via GitGitGadget" <[email protected]>