diff: teach --stat to ignore uninteresting modifications

diff.c +11 -0

+		if (DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two)) {
+			struct diffstat_file *file = 
+				diffstat->files[diffstat->nr - 1];
+			/*
+			 * Omit diffstats of modified files where nothing changed. 
+			 * Even if !same_contents, this might be the case due to
+			 * ignoring whitespace changes, etc.
+			 * 
+			 * But note that we special-case additions and deletions,
+			 * as adding an empty file, for example is still of interest.
+			 */

t/t4015-diff-whitespace.sh +1 -1

index 88d3026894..32c1b967f9 100755
@@ -789,7 +789,7 @@ test_expect_success 'checkdiff allows new blank lines' '
 	git diff --check
 '
 
-test_expect_success 'whitespace-only changes not reported' '
+test_expect_success 'whitespace-only changes not reported (diff)' '
 	git reset --hard &&
 	echo >x "hello world" &&
 	git add x &&

For example, if we further change mode bits of file 'x' (which has a whitespace-only changes applied in the test in the previous hunk), e.g.

        git update-index --chmod=+x x &&
        git diff --stat -b --cached >actual

should that be counted as a file with 0-line change that is worth reporting, or is it hidden? I _think_ the new code will do a wrong thing here. That is,

- If the change truly is only mode bits and one and two have "same_contents", the new code is bypassed, and we'll continue to show "0 lines changed, but the file is worth reporting".

- If the change is whitespace-only change plus mode bits, i.e. one and two do not have "same_contents", the new code triggers and the stat output is suppressed for the path.

From: Matthew Rogers <[email protected]>

Sometimes when diffing, files may show as being momdified even when

there are no interesting diffs to show. This happens naturally when using options such as --ignore-space-change.

We don't want to prevent
the display of all files that have 0 effective diffs since they could be the result of a rename, permission change, or other similar operation that may still be of interest so we special case additions and deletions as they are always interesting.

diff.c +10 -7

index f9709de7b4..131903fa3a 100644
@@ -3153,16 +3153,19 @@ static void show_dirstat_by_line(struct diffstat_t *data, struct diff_options *o
 	gather_dirstat(options, &dir, changed, "", 0);
 }
 
+static void free_diffstat_file(struct diffstat_file *f)
+{
+	free(f->print_name);
+	free(f->name);
+	free(f->from_name);
+	free(f);
+}
+
 void free_diffstat_info(struct diffstat_t *diffstat)
 {
 	int i;
-	for (i = 0; i < diffstat->nr; i++) {
-		struct diffstat_file *f = diffstat->files[i];
-		free(f->print_name);
-		free(f->name);
-		free(f->from_name);
-		free(f);
-	}
+	for (i = 0; i < diffstat->nr; i++)
+		free_diffstat_file(diffstat->files[i]);
 	free(diffstat->files);
 }
 

@@ -3718,6 +3721,26 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		if (xdi_diff_outf(&mf1, &mf2, discard_hunk_line,
 				  diffstat_consume, diffstat, &xpp, &xecfg))
 			die("unable to generate diffstat for %s", one->path);

diff.c +10 -0

+			 * as adding an empty file, for example is still of interest.
+			 */
+			if ((p->status == DIFF_STATUS_MODIFIED) 
+				&& !file->added
+				&& !file->deleted
+				&& one->mode == two->mode) {
+				free_diffstat_file(file);
+				diffstat->nr--;
+			}
+		}
 	}
 
 	diff_free_filespec_data(one);

t/t4015-diff-whitespace.sh +36 -2

index 88d3026894..8bdaa0a693 100755
@@ -789,7 +789,7 @@ test_expect_success 'checkdiff allows new blank lines' '
 	git diff --check
 '
 
-test_expect_success 'whitespace-only changes not reported' '
+test_expect_success 'whitespace-only changes not reported (diff)' '
 	git reset --hard &&
 	echo >x "hello world" &&
 	git add x &&

@@ -799,10 +799,44 @@ test_expect_success 'whitespace-only changes not reported' '
 	test_must_be_empty actual
 '
 
-test_expect_success 'whitespace-only changes reported across renames' '
+test_expect_success 'whitespace-only changes not reported (diffstat)' '
+	# reuse state from previous test
+	git diff --stat -b >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_success 'whitespace changes with modification reported (diffstat)' '
+	git reset --hard &&
+	echo >x "hello  world" &&
+	git update-index --chmod=+x x &&
+	git diff --stat --cached -b >actual &&
+	cat <<-EOF >expect &&
+	 x | 0
+	 1 file changed, 0 insertions(+), 0 deletions(-)
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'whitespace-only changes reported across renames (diffstat)' '
 	git reset --hard &&
 	for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
 	git add x &&
+	git commit -m "base" &&
+	sed -e "5s/^/ /" x >z &&
+	git rm x &&
+	git add z &&
+	git diff -w -M --cached --stat >actual &&
+	cat <<-EOF >expect &&
+	 x => z | 0
+	 1 file changed, 0 insertions(+), 0 deletions(-)
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'whitespace-only changes reported across renames' '
+	git reset --hard HEAD~1 &&
+	for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
+	git add x &&
 	hash_x=$(git hash-object x) &&
 	before=$(git rev-parse --short "$hash_x") &&
 	git commit -m "base" &&

base-commit: 878e727637ec5815ccb3301eb994a54df95b21b8

Quoted 3 lines · Matthew Rogers via GitGitGadget

From: Matthew Rogers <[email protected]>

Sometimes when diffing, files may show as being momdified even when

momdified? mummified? ah, modified.

Quoted 2 lines

there are no interesting diffs to show. This happens naturally when using options such as --ignore-space-change.

Read the next paragraph and notice that it explains the cases where the patch does not want not to show, and then read the above again to realize that the above does not say anything about what it wants to do to cases the next paragraph does not cover. It only says such a case often happens when --ignore-space-change is used.

When options like --ignore-space-change is in use, files with modification can have no interesting textual changes worth showing. In such cases, "git diff --stat" shows 0 lines of additions and deletions. Teach "git diff --stat" not to show such a path in its output, which would be more natural.

perhaps?

Quoted 5 lines

We don't want to prevent
the display of all files that have 0 effective diffs since they could be the result of a rename, permission change, or other similar operation that may still be of interest so we special case additions and deletions as they are always interesting.

Yup. That makes sense.

It would be nice if this does not have to be implemented as a list of exceptions, though. Rather, a more targetted "omit output only in this narrow case" would be nicer, but the check with the mode bits should do at lesat for now.

Quoted 35 lines

diff.c +10 -7

index f9709de7b4..131903fa3a 100644
@@ -3153,16 +3153,19 @@ static void show_dirstat_by_line(struct diffstat_t *data, struct diff_options *o
      gather_dirstat(options, &dir, changed, "", 0);
 }
 
+static void free_diffstat_file(struct diffstat_file *f)
+{
+     free(f->print_name);
+     free(f->name);
+     free(f->from_name);
+     free(f);
+}
+
 void free_diffstat_info(struct diffstat_t *diffstat)
 {
      int i;
-     for (i = 0; i < diffstat->nr; i++) {
-             struct diffstat_file *f = diffstat->files[i];
-             free(f->print_name);
-             free(f->name);
-             free(f->from_name);
-             free(f);
-     }
+     for (i = 0; i < diffstat->nr; i++)
+             free_diffstat_file(diffstat->files[i]);
      free(diffstat->files);
 }
 

@@ -3718,6 +3721,26 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
              if (xdi_diff_outf(&mf1, &mf2, discard_hunk_line,
                                diffstat_consume, diffstat, &xpp, &xecfg))
                      die("unable to generate diffstat for %s", one->path);

diff.c static void builtin_diffstat(const char *name_a, const char *name_b, · line 3733

Quoted 10 lines

diff.c +10 -0

+
+             if (DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two)) {
+                     struct diffstat_file *file =
+                             diffstat->files[diffstat->nr - 1];
+                     /*
+                      * Omit diffstats of modified files where nothing changed.
+                      * Even if !same_contents, this might be the case due to
+                      * ignoring whitespace changes, etc.
+                      *
+                      * But note that we special-case additions and deletions,

* renames and mode changes without any content changes,

Quoted 74 lines

diff.c +10 -0

+                      * as adding an empty file, for example is still of interest.
+                      */
+                     if ((p->status == DIFF_STATUS_MODIFIED)
+                             && !file->added
+                             && !file->deleted
+                             && one->mode == two->mode) {
+                             free_diffstat_file(file);
+                             diffstat->nr--;
+                     }
+             }
      }
 
      diff_free_filespec_data(one);

t/t4015-diff-whitespace.sh +36 -2

index 88d3026894..8bdaa0a693 100755
@@ -789,7 +789,7 @@ test_expect_success 'checkdiff allows new blank lines' '
      git diff --check
 '
 
-test_expect_success 'whitespace-only changes not reported' '
+test_expect_success 'whitespace-only changes not reported (diff)' '
      git reset --hard &&
      echo >x "hello world" &&
      git add x &&

@@ -799,10 +799,44 @@ test_expect_success 'whitespace-only changes not reported' '
      test_must_be_empty actual
 '
 
-test_expect_success 'whitespace-only changes reported across renames' '
+test_expect_success 'whitespace-only changes not reported (diffstat)' '
+     # reuse state from previous test
+     git diff --stat -b >actual &&
+     test_must_be_empty actual
+'
+
+test_expect_success 'whitespace changes with modification reported (diffstat)' '
+     git reset --hard &&
+     echo >x "hello  world" &&
+     git update-index --chmod=+x x &&
+     git diff --stat --cached -b >actual &&
+     cat <<-EOF >expect &&
+      x | 0
+      1 file changed, 0 insertions(+), 0 deletions(-)
+     EOF
+     test_cmp expect actual
+'
+
+test_expect_success 'whitespace-only changes reported across renames (diffstat)' '
      git reset --hard &&
      for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
      git add x &&
+     git commit -m "base" &&
+     sed -e "5s/^/ /" x >z &&
+     git rm x &&
+     git add z &&
+     git diff -w -M --cached --stat >actual &&
+     cat <<-EOF >expect &&
+      x => z | 0
+      1 file changed, 0 insertions(+), 0 deletions(-)
+     EOF
+     test_cmp expect actual
+'
+
+test_expect_success 'whitespace-only changes reported across renames' '
+     git reset --hard HEAD~1 &&
+     for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
+     git add x &&
      hash_x=$(git hash-object x) &&
      before=$(git rev-parse --short "$hash_x") &&
      git commit -m "base" &&

base-commit: 878e727637ec5815ccb3301eb994a54df95b21b8

Quoted 27 lines · Junio C Hamano

Quoted 3 lines · Matthew Rogers via GitGitGadget

From: Matthew Rogers <[email protected]>

Sometimes when diffing, files may show as being momdified even when

momdified? mummified? ah, modified.

Quoted 2 lines

there are no interesting diffs to show. This happens naturally when using options such as --ignore-space-change.

Read the next paragraph and notice that it explains the cases where the patch does not want not to show, and then read the above again to realize that the above does not say anything about what it wants to do to cases the next paragraph does not cover. It only says such a case often happens when --ignore-space-change is used.

When options like --ignore-space-change is in use, files with modification can have no interesting textual changes worth showing. In such cases, "git diff --stat" shows 0 lines of additions and deletions. Teach "git diff --stat" not to show such a path in its output, which would be more natural.

perhaps?

Quoted 7 lines

Quoted 5 lines

We don't want to prevent
the display of all files that have 0 effective diffs since they could be the result of a rename, permission change, or other similar operation that may still be of interest so we special case additions and deletions as they are always interesting.

Yup. That makes sense.

I'll send a reroll with the message improved as you suggested, as well as updating

Quoted 127 lines

It would be nice if this does not have to be implemented as a list of exceptions, though. Rather, a more targetted "omit output only in this narrow case" would be nicer, but the check with the mode bits should do at lesat for now.

Quoted 35 lines

diff.c +10 -7

index f9709de7b4..131903fa3a 100644
@@ -3153,16 +3153,19 @@ static void show_dirstat_by_line(struct diffstat_t *data, struct diff_options *o
      gather_dirstat(options, &dir, changed, "", 0);
 }
 
+static void free_diffstat_file(struct diffstat_file *f)
+{
+     free(f->print_name);
+     free(f->name);
+     free(f->from_name);
+     free(f);
+}
+
 void free_diffstat_info(struct diffstat_t *diffstat)
 {
      int i;
-     for (i = 0; i < diffstat->nr; i++) {
-             struct diffstat_file *f = diffstat->files[i];
-             free(f->print_name);
-             free(f->name);
-             free(f->from_name);
-             free(f);
-     }
+     for (i = 0; i < diffstat->nr; i++)
+             free_diffstat_file(diffstat->files[i]);
      free(diffstat->files);
 }
 

@@ -3718,6 +3721,26 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
              if (xdi_diff_outf(&mf1, &mf2, discard_hunk_line,
                                diffstat_consume, diffstat, &xpp, &xecfg))
                      die("unable to generate diffstat for %s", one->path);

diff.c static void builtin_diffstat(const char *name_a, const char *name_b, · line 3733

Quoted 10 lines

diff.c +10 -0

+
+             if (DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two)) {
+                     struct diffstat_file *file =
+                             diffstat->files[diffstat->nr - 1];
+                     /*
+                      * Omit diffstats of modified files where nothing changed.
+                      * Even if !same_contents, this might be the case due to
+                      * ignoring whitespace changes, etc.
+                      *
+                      * But note that we special-case additions and deletions,

* renames and mode changes without any content changes,

Quoted 73 lines

diff.c +10 -0

+                      * as adding an empty file, for example is still of interest.
+                      */
+                     if ((p->status == DIFF_STATUS_MODIFIED)
+                             && !file->added
+                             && !file->deleted
+                             && one->mode == two->mode) {
+                             free_diffstat_file(file);
+                             diffstat->nr--;
+                     }
+             }
      }
 
      diff_free_filespec_data(one);

t/t4015-diff-whitespace.sh +36 -2

index 88d3026894..8bdaa0a693 100755
@@ -789,7 +789,7 @@ test_expect_success 'checkdiff allows new blank lines' '
      git diff --check
 '
 
-test_expect_success 'whitespace-only changes not reported' '
+test_expect_success 'whitespace-only changes not reported (diff)' '
      git reset --hard &&
      echo >x "hello world" &&
      git add x &&

@@ -799,10 +799,44 @@ test_expect_success 'whitespace-only changes not reported' '
      test_must_be_empty actual
 '
 
-test_expect_success 'whitespace-only changes reported across renames' '
+test_expect_success 'whitespace-only changes not reported (diffstat)' '
+     # reuse state from previous test
+     git diff --stat -b >actual &&
+     test_must_be_empty actual
+'
+
+test_expect_success 'whitespace changes with modification reported (diffstat)' '
+     git reset --hard &&
+     echo >x "hello  world" &&
+     git update-index --chmod=+x x &&
+     git diff --stat --cached -b >actual &&
+     cat <<-EOF >expect &&
+      x | 0
+      1 file changed, 0 insertions(+), 0 deletions(-)
+     EOF
+     test_cmp expect actual
+'
+
+test_expect_success 'whitespace-only changes reported across renames (diffstat)' '
      git reset --hard &&
      for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
      git add x &&
+     git commit -m "base" &&
+     sed -e "5s/^/ /" x >z &&
+     git rm x &&
+     git add z &&
+     git diff -w -M --cached --stat >actual &&
+     cat <<-EOF >expect &&
+      x => z | 0
+      1 file changed, 0 insertions(+), 0 deletions(-)
+     EOF
+     test_cmp expect actual
+'
+
+test_expect_success 'whitespace-only changes reported across renames' '
+     git reset --hard HEAD~1 &&
+     for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
+     git add x &&
      hash_x=$(git hash-object x) &&
      before=$(git rev-parse --short "$hash_x") &&
      git commit -m "base" &&

Quoted 1 line

Quoted 1 line

base-commit: 878e727637ec5815ccb3301eb994a54df95b21b8

--
Matthew Rogers

From: Matthew Rogers <[email protected]>

When options such as --ignore-space-change are in use, files with modifications can have no interesting textual changes worth showing. In such cases, "git diff --stat" shows 0 lines of additions and deletions. Teach "git diff --stat" not to show such a path in its output, which would be more natural.

However, we don't want to prevent the display of all files that have 0 effective diffs since they could be the result of a rename, permission change, or other similar operation that may still be of interest so we special case additions and deletions as they are always interesting.

Signed-off-by Matthew Rogers <[email protected]>

---