threads / discuss / 31850

Fix "git diff --stat" for interesting - but empty - file changes

Subject: Fix "git diff --stat" for interesting - but empty - file changes

## tl;dr

3 messages between Oct 17, 2012 and Oct 17, 2012.

replies: 2people: 2as markdown or json

Linus Torvalds· Oct 17, 2012, 17:00 UTC · lore

The behavior of "git diff --stat" is rather odd for files that have zero lines of changes: it will discount them entirely unless they were renames.

Which means that the stat output will simply not show files that only had "other" changes: they were created or deleted, or their mode was changed.

Now, those changes do show up in the summary, but so do renames, so the diffstat logic is inconsistent. Why does it show renames with zero lines changed, but not mode changes or added files with zero lines changed?

So change the logic to not check for "is_renamed", but for "is_interesting" instead, where "interesting" is judged to be any action but a pure data change (because a pure data change with zero data changed really isn't worth showing, if we ever get one in our diffpairs).

So if you did
   chmod +x Makefile
   git diff --stat
before, it would show empty (" 0 files changed"), with this it shows
 Makefile | 0
 1 file changed, 0 insertions(+), 0 deletions(-)

which I think is a more correct diffstat (and then with "--summary" it shows *what* the metadata change to Makefile was - this is completely consistent with our handling of renamed files).

Side note: the old behavior was *really* odd. With no changes at all, "git diff --stat" output was empty. With just a chmod, it said "0 files changed". No way is our legacy behavior sane.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

This was triggered by kernel developers not noticing that they had added zero-sized files, because those additions never showed up in the diffstat.

NOTE! This does break two of our tests, so we clearly did this on purpose, or at least tested for it. I just uncommented the subtests that this makes irrelevant, and changed the output of another one.

Another test was simply buggy. It used "git diff --root cmit", and thought that would be the diff against root. It isn't, and never has been. It just happened to give the same (no file) output before. Fixing --stat to show new files showed how buggy the test was. The "--root" thing matters for "git show" or "git log" (when showing a root commit) and for "git diff-tree" with a single tree.

Maybe we would *want* to make "git diff --root <cmit>" be the "diff between root and cmit", but that's not what it actually is.

Comments?
 diff.c                        | 25 +++++++++++++----------
 t/t4006-diff-mode.sh          | 46 +++++++++++++++++++++----------------------
 t/t4049-diff-stat-count.sh    |  3 ++-
 t/t4205-log-pretty-formats.sh |  4 ++--
 4 files changed, 42 insertions(+), 36 deletions(-)
diff --git a/diff.c b/diff.c
index 35d3f073859a..95bbad66c686 100644
--- a/diff.c
+++ b/diff.c
@@ -1300,6 +1300,7 @@ struct diffstat_t {
 		unsigned is_unmerged:1;
 		unsigned is_binary:1;
 		unsigned is_renamed:1;
+		unsigned is_interesting:1;
 		uintmax_t added, deleted;
 	} **files;
 };
@@ -1469,7 +1470,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	for (i = 0; (i < count) && (i < data->nr); i++) {
 		struct diffstat_file *file = data->files[i];
 		uintmax_t change = file->added + file->deleted;
-		if (!data->files[i]->is_renamed &&
+		if (!data->files[i]->is_interesting &&
 			 (change == 0)) {
 			count++; /* not shown == room for one more */
 			continue;
@@ -1590,7 +1591,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		uintmax_t deleted = data->files[i]->deleted;
 		int name_len;
 
-		if (!data->files[i]->is_renamed &&
+		if (!data->files[i]->is_interesting &&
 			 (added + deleted == 0)) {
 			total_files--;
 			continue;
@@ -1669,7 +1670,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	for (i = count; i < data->nr; i++) {
 		uintmax_t added = data->files[i]->added;
 		uintmax_t deleted = data->files[i]->deleted;
-		if (!data->files[i]->is_renamed &&
+		if (!data->files[i]->is_interesting &&
 			 (added + deleted == 0)) {
 			total_files--;
 			continue;
@@ -1697,7 +1698,7 @@ static void show_shortstats(struct diffstat_t *data, struct diff_options *option
 
 		if (data->files[i]->is_unmerged)
 			continue;
-		if (!data->files[i]->is_renamed && (added + deleted == 0)) {
+		if (!data->files[i]->is_interesting && (added + deleted == 0)) {
 			total_files--;
 		} else if (!data->files[i]->is_binary) { /* don't count bytes */
 			adds += added;
@@ -2397,13 +2398,20 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 			     struct diff_filespec *two,
 			     struct diffstat_t *diffstat,
 			     struct diff_options *o,
-			     int complete_rewrite)
+			     struct diff_filepair *p)
 {
 	mmfile_t mf1, mf2;
 	struct diffstat_file *data;
 	int same_contents;
+	int complete_rewrite = 0;
+
+	if (!DIFF_PAIR_UNMERGED(p)) {
+		if (p->status == DIFF_STATUS_MODIFIED && p->score)
+			complete_rewrite = 1;
+	}
 
 	data = diffstat_add(diffstat, name_a, name_b);
+	data->is_interesting = p->status != 0;
 
 	if (!one || !two) {
 		data->is_unmerged = 1;
@@ -3114,11 +3122,10 @@ static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
 {
 	const char *name;
 	const char *other;
-	int complete_rewrite = 0;
 
 	if (DIFF_PAIR_UNMERGED(p)) {
 		/* unmerged */
-		builtin_diffstat(p->one->path, NULL, NULL, NULL, diffstat, o, 0);
+		builtin_diffstat(p->one->path, NULL, NULL, NULL, diffstat, o, p);
 		return;
 	}
 
@@ -3131,9 +3138,7 @@ static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
 	diff_fill_sha1_info(p->one);
 	diff_fill_sha1_info(p->two);
 
-	if (p->status == DIFF_STATUS_MODIFIED && p->score)
-		complete_rewrite = 1;
-	builtin_diffstat(name, other, p->one, p->two, diffstat, o, complete_rewrite);
+	builtin_diffstat(name, other, p->one, p->two, diffstat, o, p);
 }
 
 static void run_checkdiff(struct diff_filepair *p, struct diff_options *o)
diff --git a/t/t4006-diff-mode.sh b/t/t4006-diff-mode.sh
index 3d4b1ba23f9e..05911492ca6d 100755
--- a/t/t4006-diff-mode.sh
+++ b/t/t4006-diff-mode.sh
@@ -32,28 +32,28 @@ test_expect_success 'prepare binary file' '
 	git commit -m binbin
 '
 
-test_expect_success '--stat output after text chmod' '
-	test_chmod -x rezrov &&
-	echo " 0 files changed" >expect &&
-	git diff HEAD --stat >actual &&
-	test_i18ncmp expect actual
-'
-
-test_expect_success '--shortstat output after text chmod' '
-	git diff HEAD --shortstat >actual &&
-	test_i18ncmp expect actual
-'
-
-test_expect_success '--stat output after binary chmod' '
-	test_chmod +x binbin &&
-	echo " 0 files changed" >expect &&
-	git diff HEAD --stat >actual &&
-	test_i18ncmp expect actual
-'
-
-test_expect_success '--shortstat output after binary chmod' '
-	git diff HEAD --shortstat >actual &&
-	test_i18ncmp expect actual
-'
+# test_expect_success '--stat output after text chmod' '
+# 	test_chmod -x rezrov &&
+# 	echo " 0 files changed" >expect &&
+# 	git diff HEAD --stat >actual &&
+#	test_i18ncmp expect actual
+# '
+#
+# test_expect_success '--shortstat output after text chmod' '
+# 	git diff HEAD --shortstat >actual &&
+# 	test_i18ncmp expect actual
+# '
+#
+# test_expect_success '--stat output after binary chmod' '
+# 	test_chmod +x binbin &&
+# 	echo " 0 files changed" >expect &&
+# 	git diff HEAD --stat >actual &&
+# 	test_i18ncmp expect actual
+# '
+#
+# test_expect_success '--shortstat output after binary chmod' '
+# 	git diff HEAD --shortstat >actual &&
+# 	test_i18ncmp expect actual
+# '
 
 test_done
diff --git a/t/t4049-diff-stat-count.sh b/t/t4049-diff-stat-count.sh
index b41eb61ca8b1..7b3ef00533f7 100755
--- a/t/t4049-diff-stat-count.sh
+++ b/t/t4049-diff-stat-count.sh
@@ -16,7 +16,8 @@ test_expect_success setup '
 	cat >expect <<-\EOF
 	 a | 1 +
 	 b | 1 +
-	 2 files changed, 2 insertions(+)
+	 ...
+	 4 files changed, 2 insertions(+)
 	EOF
 	git diff --stat --stat-count=2 >actual &&
 	test_i18ncmp expect actual
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 2c45de7aeaf2..98a43d457a3d 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -85,7 +85,7 @@ test_expect_success 'NUL termination' '
 
 test_expect_success 'NUL separation with --stat' '
 	stat0_part=$(git diff --stat HEAD^ HEAD) &&
-	stat1_part=$(git diff --stat --root HEAD^) &&
+	stat1_part=$(git diff-tree --no-commit-id --stat --root HEAD^) &&
 	printf "add bar\n$stat0_part\n\0initial\n$stat1_part\n" >expected &&
 	git log -z --stat --pretty="format:%s" >actual &&
 	test_i18ncmp expected actual
@@ -93,7 +93,7 @@ test_expect_success 'NUL separation with --stat' '
 
 test_expect_failure 'NUL termination with --stat' '
 	stat0_part=$(git diff --stat HEAD^ HEAD) &&
-	stat1_part=$(git diff --stat --root HEAD^) &&
+	stat1_part=$(git diff-tree --no-commit-id --stat --root HEAD^) &&
 	printf "add bar\n$stat0_part\n\0initial\n$stat1_part\n\0" >expected &&
 	git log -z --stat --pretty="tformat:%s" >actual &&
 	test_i18ncmp expected actual
Junio C Hamano· Oct 17, 2012, 18:28 UTC · re: Linus Torvalds · lore

Re: Fix "git diff --stat" for interesting - but empty - file changes

Linus Torvalds <torvalds@linux-foundation.org> writes:
Show 26 quoted lines
> So if you did
>
>    chmod +x Makefile
>    git diff --stat
>
> before, it would show empty (" 0 files changed"), with this it shows
>
>  Makefile | 0
>  1 file changed, 0 insertions(+), 0 deletions(-)
>
> which I think is a more correct diffstat (and then with "--summary" it
> shows *what* the metadata change to Makefile was - this is completely
> consistent with our handling of renamed files).
>
> Side note: the old behavior was *really* odd. With no changes at all,
> "git diff --stat" output was empty. With just a chmod, it said "0
> files changed". No way is our legacy behavior sane.
>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
>
> This was triggered by kernel developers not noticing that they had
> added zero-sized files, because those additions never showed up in the
> diffstat.
> ...
> Comments?

I think listing a file whose content remain unchanged with 0 as the number of lines affected makes sense, and it will mesh well with Duy's

  http://thread.gmane.org/gmane.comp.version-control.git/207749

I first wondered if we would get a division-by-zero while scaling the graph, but we do not scale smaller numbers up to fill the columns, so we should be safe.

These days, we omit 0 insertions and 0 deletions, so I am not sure what you should get for this case, though:

>  Makefile | 0
>  1 file changed, 0 insertions(+), 0 deletions(-)
Should we just say "1 file changed"?
Linus Torvalds· Oct 17, 2012, 19:35 UTC · re: Junio C Hamano · lore

Re: Fix "git diff --stat" for interesting - but empty - file changes

On Wed, Oct 17, 2012 at 11:28 AM, Junio C Hamano <gitster@pobox.com> wrote:
Show 10 quoted lines
>
> I think listing a file whose content remain unchanged with 0 as the
> number of lines affected makes sense, and it will mesh well with
> Duy's
>
>   http://thread.gmane.org/gmane.comp.version-control.git/207749
>
> I first wondered if we would get a division-by-zero while scaling
> the graph, but we do not scale smaller numbers up to fill the
> columns, so we should be safe.

Note that we should be safe for a totally different - and more fundamental - reason: the zero line case is by no means new. We've always done it for the rename case.

Show 7 quoted lines
> These days, we omit 0 insertions and 0 deletions, so I am not sure
> what you should get for this case, though:
>
>>  Makefile | 0
>>  1 file changed, 0 insertions(+), 0 deletions(-)
>
> Should we just say "1 file changed"?

If that is what it does for the rename case, then yes. I think it should fall out naturally.

              Linus

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