Re: bug with git-diff --quiet
On Thu, Jan 23, 2014 at 11:45:25AM +0900, IWAMOTO Toshihiro wrote:
Show 16 quoted lines
> I found "git-diff --quiet" returns a zero exit status even if there's
> a change. The following sequence reproduces the bug:
>
> $ mkdir foo
> $ cd foo
> $ git init
> $ echo a > a.txt
> $ echo b >b.txt
> $ git add ?.txt
> $ git commit
> $ echo b >> b.txt
> $ touch a.txt
> $ git diff --quiet; echo $?
>
> Interestingly, if you issue "git-diff --quiet" again, it returns the
> expected exit status 1.
Because stat info in index is updated and diff_change() won't be called again on a.txt.
Show 9 quoted lines
> The problem is in the optimization code in run_diff_files(). The
> function finds a.txt has different stat(2) data from .git/index and
> calls diff_change(), which sets DIFF_OPT_HAS_CHANGES. As the flag
> makes diff_can_quit_early() return 1, run_diff_files()'s loop finishes
> without calling diff_change() for b.txt.
>
> Then, diffcore_std() examines diff_queued_diff and clears
> DIFF_OPT_HAS_CHANGES, because a.txt is unchanged.
> This is how a change in b.txt is ignored by git-diff --quiet.
Thanks for the analysis. Perhaps we could make diff_change test whether a.txt is unchanged so it does not set HAS_CHANGES prematurely? Maybe something like below.
By the time diffcore_skip_stat_unmatch() is called, everything is cached, so there's not much of performance regression. We still do memcmp() twice (in diff_filespec_is_identical), but I think that has less impact than removing diff_can_quit_early().
-- 8< --
diff --git a/diff.c b/diff.c
index 6b4cd0e..5226fc0 100644
--- a/diff.c
+++ b/diff.c
@@ -4697,6 +4697,33 @@ 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)
+{
+ /*
+ * 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) */
+ return 1;
+ return 0;
+}
+
static void diffcore_skip_stat_unmatch(struct diff_options *diffopt)
{
int i;
@@ -4707,27 +4734,7 @@ 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 +4897,7 @@ 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 +4924,17 @@ 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)
-- 8< --
> Here's a obvious fix for this bug, but I think you can find a better
> fix. Thanks in advance.
>
>
> diff --git a/diff-lib.c b/diff-lib.c
> index 346cac6..0b8c58d 100644
> --- a/diff-lib.c
> +++ b/diff-lib.c
> @@ -105,9 +105,6 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
> int changed;
> unsigned dirty_submodule = 0;
>
> - if (diff_can_quit_early(&revs->diffopt))
> - break;
> -
> if (!ce_path_match(ce, &revs->prune_data))
> continue;
>
> --
> IWAMOTO Toshihiro
