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[PATCH] diff: report modified binary files as changes in builtin_diff()

From
René Scharfe <l.s.r@web.de>
Date
Sep 21, 2024, 15:09 UTC
Message-ID
<500a8e0a-9fbd-4b7b-b2f2-026a4293bc9f@web.de>
In-Reply-To
<CACpkL8WsNqhQ7SP27-XQwp1bzKjyUT6m2idFarZ2Z5rLVYg4pQ@mail.gmail.com>

The diff machinery has two ways to detect changes to set the exit code: Just comparing hashes and comparing blob contents. The latter is needed if certain changes have to be ignored, e.g. with --ignore-space-change or --ignore-matching-lines. It's enabled by the diff_options flag diff_from_contents.

The code for handling binary files added by 1aaf69e669 (diff: shortcut for diff'ing two binary SHA-1 objects, 2014-08-16) always uses a quick hash-only comparison, even if the slow way is taken. We need it to report a hash difference as a change for the purpose of setting the exit code, though, but it never did. Fix that.

d7b97b7185 (diff: let external diffs report that changes are uninteresting, 2024-06-09) set diff_from_contents if external diff programs are allowed. This is the default e.g. for git diff, and so that change exposed the inconsistency much more widely.

Reported-by: Kohei Shibata <shiba200712@gmail.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
---
Thank you for the report!
 diff.c                 | 1 +
 t/t4017-diff-retval.sh | 8 ++++++++
 2 files changed, 9 insertions(+)
diff --git a/diff.c b/diff.c
index 3be927b073..84a6bb0868 100644
--- a/diff.c
+++ b/diff.c
@@ -3675,6 +3675,7 @@ static void builtin_diff(const char *name_a,
 			emit_diff_symbol(o, DIFF_SYMBOL_BINARY_FILES,
 					 sb.buf, sb.len, 0);
 			strbuf_release(&sb);
+			o->found_changes = 1;
 			goto free_ab_and_return;
 		}
 		if (fill_mmfile(o->repo, &mf1, one) < 0 ||
diff --git a/t/t4017-diff-retval.sh b/t/t4017-diff-retval.sh
index d644310e22..1cea73ef5a 100755
--- a/t/t4017-diff-retval.sh
+++ b/t/t4017-diff-retval.sh
@@ -145,6 +145,14 @@ test_expect_success 'option errors are not confused by --exit-code' '

 for option in --exit-code --quiet
 do
+	test_expect_success "git diff $option returns 1 for changed binary file" "
+		test_when_finished 'rm -f .gitattributes' &&
+		git reset --hard &&
+		echo a binary >.gitattributes &&
+		echo 2 >>a &&
+		test_expect_code 1 git diff $option
+	"
+
 	test_expect_success "git diff $option returns 1 for copied file" "
 		git reset --hard &&
 		cp a copy &&
--
2.46.0
Previous: Kohei ShibataNext: Thomas Braun
Message 2 of 4 in “git diff --exit-code returns 0 when binary files differ”
  1. Kohei ShibataSep 21, 2024
  2. diff: report modified binary files as changes in builtin_diff()René Scharfe, Sep 21, 2024
  3. Thomas BraunSep 25, 2024
  4. Junio C HamanoSep 25, 2024

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