diff: ensure consistent diff behavior with ignore options
In git-diff, options like `-w` and `-I<regex>`, two files are considered equivalent under the specified "ignore" rules, even when they are not bit-for-bit identical. For options like `--raw`, `--name-status`, and `--name-only`, git-diff deliberately compares only the SHA values to determine whether two files are equivalent, for performance reasons. As a result, a file shown in `git diff --name-status` may not appear in `git diff --patch`. To quickly determine whether two files are equivalent, add a helper function diff_flush_patch_quietly() in diff.c. Add `.dry_run` field in `struct diff_options`. When `.dry_run` is true, builtin_diff() returns immediately upon finding any change. Call diff_flush_patch_quietly() to determine if we should flush `--raw`, `--name-only` or `--name-status` output. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Lidong Yan <yldhome2d2@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Lidong Yan committed
Aug 8, 2025 at 11:30 UTC
b55e6d36ebce69136559add8fffd1a65df231518
5 files changed
+70
-23
diff.c
+50
-14
@@ -2444,6 +2444,15 @@ static int fn_out_consume(void *priv, char *line, unsigned long len)
2444
return 0;
2445
}
2446
2447
+static int quick_consume(void *priv, char *line UNUSED, unsigned long len UNUSED)
2448
+{
2449
+ struct emit_callback *ecbdata = priv;
2450
+ struct diff_options *o = ecbdata->opt;
2451
+
2452
+ o->found_changes = 1;
2453
+ return 1;
2454
+}
2455
+
2456
static void pprint_rename(struct strbuf *name, const char *a, const char *b)
2457
{
2458
const char *old_name = a;
@@ -3759,8 +3768,21 @@ static void builtin_diff(const char *name_a,
3768
3769
if (o->word_diff)
3770
init_diff_words_data(&ecbdata, o, one, two);
3762
- if (xdi_diff_outf(&mf1, &mf2, NULL, fn_out_consume,
3763
- &ecbdata, &xpp, &xecfg))
3771
+ if (o->dry_run) {
3772
+ /*
3773
+ * Unlike the !dry_run case, we need to ignore the
3774
+ * return value from xdi_diff_outf() here, because
3775
+ * xdi_diff_outf() takes non-zero return from its
3776
+ * callback function as a sign of error and returns
3777
+ * early (which is why we return non-zero from our
3778
+ * callback, quick_consume()). Unfortunately,
3779
+ * xdi_diff_outf() signals an error by returning
3780
+ * non-zero.
3781
+ */
3782
+ xdi_diff_outf(&mf1, &mf2, NULL, quick_consume,
3783
+ &ecbdata, &xpp, &xecfg);
3784
+ } else if (xdi_diff_outf(&mf1, &mf2, NULL, fn_out_consume,
3785
+ &ecbdata, &xpp, &xecfg))
3786
die("unable to generate diff for %s", one->path);
3787
if (o->word_diff)
3788
free_diff_words_data(&ecbdata);
@@ -6150,6 +6172,22 @@ static void diff_flush_patch(struct diff_filepair *p, struct diff_options *o)
6172
run_diff(p, o);
6173
}
6174
6175
+/* return 1 if any change is found; otherwise, return 0 */
6176
+static int diff_flush_patch_quietly(struct diff_filepair *p, struct diff_options *o)
6177
+{
6178
+ int saved_dry_run = o->dry_run;
6179
+ int saved_found_changes = o->found_changes;
6180
+ int ret;
6181
+
6182
+ o->dry_run = 1;
6183
+ o->found_changes = 0;
6184
+ diff_flush_patch(p, o);
6185
+ ret = o->found_changes;
6186
+ o->dry_run = saved_dry_run;
6187
+ o->found_changes |= saved_found_changes;
6188
+ return ret;
6189
+}
6190
+
6191
static void diff_flush_stat(struct diff_filepair *p, struct diff_options *o,
6192
struct diffstat_t *diffstat)
6193
{
@@ -6778,8 +6816,15 @@ void diff_flush(struct diff_options *options)
6816
DIFF_FORMAT_CHECKDIFF)) {
6817
for (i = 0; i < q->nr; i++) {
6818
struct diff_filepair *p = q->queue[i];
6781
- if (check_pair_status(p))
6782
- flush_one_pair(p, options);
6819
+
6820
+ if (!check_pair_status(p))
6821
+ continue;
6822
+
6823
+ if (options->flags.diff_from_contents &&
6824
+ !diff_flush_patch_quietly(p, options))
6825
+ continue;
6826
+
6827
+ flush_one_pair(p, options);
6828
}
6829
separator++;
6830
}
@@ -6831,19 +6876,10 @@ void diff_flush(struct diff_options *options)
6876
if (output_format & DIFF_FORMAT_NO_OUTPUT &&
6877
options->flags.exit_with_status &&
6878
options->flags.diff_from_contents) {
6834
- /*
6835
- * run diff_flush_patch for the exit status. setting
6836
- * options->file to /dev/null should be safe, because we
6837
- * aren't supposed to produce any output anyway.
6838
- */
6839
- diff_free_file(options);
6840
- options->file = xfopen("/dev/null", "w");
6841
- options->close_file = 1;
6842
- options->color_moved = 0;
6879
for (i = 0; i < q->nr; i++) {
6880
struct diff_filepair *p = q->queue[i];
6881
if (check_pair_status(p))
6846
- diff_flush_patch(p, options);
6882
+ diff_flush_patch_quietly(p, options);
6883
if (options->found_changes)
6884
break;
6885
}
diff.h
+2
@@ -400,6 +400,8 @@ struct diff_options {
400
#define COLOR_MOVED_WS_ERROR (1<<0)
401
unsigned color_moved_ws_handling;
402
403
+ bool dry_run;
404
+
405
struct repository *repo;
406
struct strmap *additional_path_headers;
407
t/t4013-diff-various.sh
+13
@@ -648,6 +648,19 @@ test_expect_success 'diff -I<regex>: detect malformed regex' '
648
test_grep "invalid regex given to -I: " error
649
'
650
651
+test_expect_success 'diff -I<regex>: ignore matching file' '
652
+ test_when_finished "git rm -f file1" &&
653
+ test_seq 50 >file1 &&
654
+ git add file1 &&
655
+ test_seq 50 | sed -e "s/13/ten and three/" -e "s/^[124-9].*/& /" >file1 &&
656
+
657
+ : >actual &&
658
+ git diff --raw --ignore-blank-lines -I"ten.*e" -I"^[124-9]" >>actual &&
659
+ git diff --name-only --ignore-blank-lines -I"ten.*e" -I"^[124-9]" >>actual &&
660
+ git diff --name-status --ignore-blank-lines -I"ten.*e" -I"^[124-9]" >>actual &&
661
+ test_grep ! "file1" actual
662
+'
663
+
664
# check_prefix <patch> <src> <dst>
665
# check only lines with paths to avoid dependency on exact oid/contents
666
check_prefix () {
t/t4015-diff-whitespace.sh
+2
-6
@@ -11,12 +11,8 @@ test_description='Test special whitespace in diff engine.
11
. "$TEST_DIRECTORY"/lib-diff.sh
12
13
for opt_res in --patch --quiet -s --stat --shortstat --dirstat=lines \
14
- --raw! --name-only! --name-status!
14
+ --raw --name-only --name-status
15
do
16
- opts=${opt_res%!} expect_failure=
17
- test "$opts" = "$opt_res" ||
18
- expect_failure="test_expect_code 1"
19
-
16
test_expect_success "status with $opts (different)" '
17
echo foo >x &&
18
git add x &&
@@ -43,7 +39,7 @@ do
39
echo foo >x &&
40
git add x &&
41
echo " foo" >x &&
46
- $expect_failure git diff -w $opts --exit-code x
42
+ git diff -w $opts --exit-code x
43
'
44
done
45
xdiff-interface.h
+3
-3
@@ -28,9 +28,9 @@
28
* from an error internal to xdiff, xdiff itself will see that
29
* non-zero return and translate it to -1.
30
*
31
- * See "diff_grep" in diffcore-pickaxe.c for a trick to work around
32
- * this, i.e. using the "consume_callback_data" to note the desired
33
- * early return.
31
+ * See "diff_grep" in diffcore-pickaxe.c and "quick_consume" in diff.c
32
+ * for a trick to work around this, i.e. using the "consume_callback_data"
33
+ * to note the desired early return.
34
*/
35
typedef int (*xdiff_emit_line_fn)(void *, char *, unsigned long);
36
typedef void (*xdiff_emit_hunk_fn)(void *data,