diff: teach --stat to ignore uninteresting modifications

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 <mattr94@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index d24aaa304780b7105618434d80a76627e588d280..810c5139953f7ac62f64a32371b0b0e359c4acef 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -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 +3721,27 @@ 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);
+
+               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, deletions,
+                        * renames, and mode changes 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);

diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 88d3026894f87f4d86cb6f4178898b6879630e73..8bdaa0a693fa52adf2314d5777a195d035d6009c 100755 (executable)
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -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" &&