Merge branch 'nd/diff-quiet-stat-dirty' into maint

"git diff --quiet -- pathspec1 pathspec2" sometimes did not return
correct status value.

* nd/diff-quiet-stat-dirty:
  diff: do not quit early on stat-dirty files
  diff.c: move diffcore_skip_stat_unmatch core logic out for reuse later

diff.c

@@ -4697,6 +4697,38 @@ static int diff_filespec_is_identical(struct diff_filespec *one,
 	return !memcmp(one->data, two->data, one->size);
 }
 
+static int diff_filespec_check_stat_unmatch(struct diff_filepair *p)
+{
+	if (p->done_skip_stat_unmatch)
+		return p->skip_stat_unmatch_result;
+
+	p->done_skip_stat_unmatch = 1;
+	p->skip_stat_unmatch_result = 0;
+	/*
+	 * 1. Entries that come from stat info dirtiness
+	 *    always have both sides (iow, not create/delete),
+	 *    one side of the object name is unknown, with
+	 *    the same mode and size.  Keep the ones that
+	 *    do not match these criteria.  They have real
+	 *    differences.
+	 *
+	 * 2. At this point, the file is known to be modified,
+	 *    with the same mode and size, and the object
+	 *    name of one side is unknown.  Need to inspect
+	 *    the identical contents.
+	 */
+	if (!DIFF_FILE_VALID(p->one) || /* (1) */
+	    !DIFF_FILE_VALID(p->two) ||
+	    (p->one->sha1_valid && p->two->sha1_valid) ||
+	    (p->one->mode != p->two->mode) ||
+	    diff_populate_filespec(p->one, 1) ||
+	    diff_populate_filespec(p->two, 1) ||
+	    (p->one->size != p->two->size) ||
+	    !diff_filespec_is_identical(p->one, p->two)) /* (2) */
+		p->skip_stat_unmatch_result = 1;
+	return p->skip_stat_unmatch_result;
+}
+
 static void diffcore_skip_stat_unmatch(struct diff_options *diffopt)
 {
 	int i;
@@ -4707,27 +4739,7 @@ static void diffcore_skip_stat_unmatch(struct diff_options *diffopt)
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filepair *p = q->queue[i];
 
-		/*
-		 * 1. Entries that come from stat info dirtiness
-		 *    always have both sides (iow, not create/delete),
-		 *    one side of the object name is unknown, with
-		 *    the same mode and size.  Keep the ones that
-		 *    do not match these criteria.  They have real
-		 *    differences.
-		 *
-		 * 2. At this point, the file is known to be modified,
-		 *    with the same mode and size, and the object
-		 *    name of one side is unknown.  Need to inspect
-		 *    the identical contents.
-		 */
-		if (!DIFF_FILE_VALID(p->one) || /* (1) */
-		    !DIFF_FILE_VALID(p->two) ||
-		    (p->one->sha1_valid && p->two->sha1_valid) ||
-		    (p->one->mode != p->two->mode) ||
-		    diff_populate_filespec(p->one, 1) ||
-		    diff_populate_filespec(p->two, 1) ||
-		    (p->one->size != p->two->size) ||
-		    !diff_filespec_is_identical(p->one, p->two)) /* (2) */
+		if (diff_filespec_check_stat_unmatch(p))
 			diff_q(&outq, p);
 		else {
 			/*
@@ -4890,6 +4902,7 @@ void diff_change(struct diff_options *options,
 		 unsigned old_dirty_submodule, unsigned new_dirty_submodule)
 {
 	struct diff_filespec *one, *two;
+	struct diff_filepair *p;
 
 	if (S_ISGITLINK(old_mode) && S_ISGITLINK(new_mode) &&
 	    is_submodule_ignored(concatpath, options))
@@ -4916,10 +4929,16 @@ void diff_change(struct diff_options *options,
 	fill_filespec(two, new_sha1, new_sha1_valid, new_mode);
 	one->dirty_submodule = old_dirty_submodule;
 	two->dirty_submodule = new_dirty_submodule;
+	p = diff_queue(&diff_queued_diff, one, two);
 
-	diff_queue(&diff_queued_diff, one, two);
-	if (!DIFF_OPT_TST(options, DIFF_FROM_CONTENTS))
-		DIFF_OPT_SET(options, HAS_CHANGES);
+	if (DIFF_OPT_TST(options, DIFF_FROM_CONTENTS))
+		return;
+
+	if (DIFF_OPT_TST(options, QUICK) && options->skip_stat_unmatch &&
+	    !diff_filespec_check_stat_unmatch(p))
+		return;
+
+	DIFF_OPT_SET(options, HAS_CHANGES);
 }
 
 struct diff_filepair *diff_unmerge(struct diff_options *options, const char *path)

diffcore.h

@@ -68,6 +68,8 @@ struct diff_filepair {
 	unsigned broken_pair : 1;
 	unsigned renamed_pair : 1;
 	unsigned is_unmerged : 1;
+	unsigned done_skip_stat_unmatch : 1;
+	unsigned skip_stat_unmatch_result : 1;
 };
 #define DIFF_PAIR_UNMERGED(p) ((p)->is_unmerged)
 

t/t4035-diff-quiet.sh

@@ -148,4 +148,10 @@ test_expect_success 'git diff --ignore-all-space, both files outside repo' '
 	)
 '
 
+test_expect_success 'git diff --quiet ignores stat-change only entries' '
+	test-chmtime +10 a &&
+	echo modified >>b &&
+	test_expect_code 1 git diff --quiet
+'
+
 test_done