[PATCH v5] submodule: use the submodule repository to abbreviate commits

From: Srujith A Poojary via GitGitGadget <gitgitgadget@gmail.com>
Date: Nov 4, 2026, 03:43 UTC
Message-ID: <pull.2288.v5.git.1793763781129.gitgitgadget@gmail.com>
In-Reply-To: <pull.2288.git.1793435149942.gitgitgadget@gmail.com>

From: Srujith A Poojary <poojarysrujith@gmail.com>

The commit IDs shown in a submodule diff header belong to the submodule's object database. However, strbuf_add_unique_abbrev() uses the_repository, so it checks the superproject's object database when abbreviating those IDs.

Use the submodule repository when it is available, and fall back to the repository from the diff options when it is not.

The expected abbreviation for a submodule commit depends on the repository's hash algorithm. Use test_oid_cache to provide the expected value for each algorithm and remove the SHA1 prerequisite so this test runs with both SHA-1 and SHA-256.

Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
---
    [Outreachy PATCH] t4041: use submodule repository for commit
    abbreviations

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2288%2Fpoojarysrujith%2Fmicroproject-git-libification-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2288/poojarysrujith/microproject-git-libification-v5
Pull-Request: https://github.com/gitgitgadget/git/pull/2288

Range-diff vs v4:

 1:  a8c54b9292 ! 1:  f94aa2476f submodule: use the submodule repository to abbreviate commits
     @@ Commit message
          Use the submodule repository when it is available, and fall back
          to the repository from the diff options when it is not.
      
     +    The expected abbreviation for a submodule commit depends on the
     +    repository's hash algorithm. Use test_oid_cache to provide the
     +    expected value for each algorithm and remove the SHA1 prerequisite
     +    so this test runs with both SHA-1 and SHA-256.
     +
          Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
      
       ## submodule.c ##
     @@ t/t4041-diff-submodule-option.sh: export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
       
       . ./test-lib.sh
       
     -+test_expect_success SHA1 'submodule commit abbreviation uses submodule object database' '
     ++test_expect_success 'submodule commit abbreviation uses submodule object database' '
     ++	test_oid_cache <<-EOF &&
     ++	submodule_commit1_abbrev sha1:0000000000e
     ++	submodule_commit1_abbrev sha256:24c81a5
     ++	EOF
      +	test_when_finished "rm -rf collision-super" &&
      +	git init -q collision-super &&
      +	git init -q collision-super/sm1 &&
     @@ t/t4041-diff-submodule-option.sh: export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
      +	git -C collision-super update-index --add --cacheinfo 160000,"$commit1",sm1 &&
      +	git -C collision-super commit -q -m "Add submodule" &&
      +	git -C collision-super diff --submodule=log >actual &&
     -+	printf "Submodule sm1 0000000000e..%s:\n  > child\n" \
     ++	printf "Submodule sm1 %s..%s:\n  > child\n" \
     ++		"$(test_oid submodule_commit1_abbrev)" \
      +		"$(git -C collision-super/sm1 rev-parse --short "$commit2")" >expected &&
      +	test_cmp expected actual
      +'
 2:  99a1234544 < -:  ---------- t4041: test SHA-256 submodule abbreviations

 submodule.c                      |  5 +++--
 t/t4041-diff-submodule-option.sh | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/submodule.c b/submodule.c
index 6fcb606f7e..1302c11ddf 100644
--- a/submodule.c
+++ b/submodule.c
@@ -543,6 +543,7 @@ static void show_submodule_header(struct diff_options *o,
 		struct commit **left, struct commit **right,
 		struct commit_list **merge_bases)
 {
+	struct repository *repo = sub ? sub : o->repo;
 	const char *message = NULL;
 	struct strbuf sb = STRBUF_INIT;
 	int fast_forward = 0, fast_backward = 0;
@@ -599,9 +600,9 @@ static void show_submodule_header(struct diff_options *o,
 
 output_header:
 	strbuf_addf(&sb, "Submodule %s ", path);
-	strbuf_add_unique_abbrev(&sb, one, DEFAULT_ABBREV);
+	strbuf_repo_add_unique_abbrev(&sb, repo, one, DEFAULT_ABBREV);
 	strbuf_addstr(&sb, (fast_backward || fast_forward) ? ".." : "...");
-	strbuf_add_unique_abbrev(&sb, two, DEFAULT_ABBREV);
+	strbuf_repo_add_unique_abbrev(&sb, repo, two, DEFAULT_ABBREV);
 	if (message)
 		strbuf_addf(&sb, " %s\n", message);
 	else
diff --git a/t/t4041-diff-submodule-option.sh b/t/t4041-diff-submodule-option.sh
index 4dd4954260..4539d6bba5 100755
--- a/t/t4041-diff-submodule-option.sh
+++ b/t/t4041-diff-submodule-option.sh
@@ -14,6 +14,29 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
 . ./test-lib.sh
 
+test_expect_success 'submodule commit abbreviation uses submodule object database' '
+	test_oid_cache <<-EOF &&
+	submodule_commit1_abbrev sha1:0000000000e
+	submodule_commit1_abbrev sha256:24c81a5
+	EOF
+	test_when_finished "rm -rf collision-super" &&
+	git init -q collision-super &&
+	git init -q collision-super/sm1 &&
+	printf "0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n\nb1rwzyc3\n" >collision-super/sm1/a0blgqsjc &&
+	git -C collision-super/sm1 add a0blgqsjc &&
+	tree=$(git -C collision-super/sm1 write-tree) &&
+	commit1=$(GIT_AUTHOR_DATE="1112911993 -0700" GIT_COMMITTER_DATE="1112911993 -0700" git -C collision-super/sm1 commit-tree "$tree" -m a2onsxbvj) &&
+	commit2=$(printf "child\n" | GIT_AUTHOR_DATE="1112912053 -0700" GIT_COMMITTER_DATE="1112912053 -0700" git -C collision-super/sm1 commit-tree "$tree" -p "$commit1") &&
+	git -C collision-super/sm1 checkout -q "$commit2" &&
+	git -C collision-super update-index --add --cacheinfo 160000,"$commit1",sm1 &&
+	git -C collision-super commit -q -m "Add submodule" &&
+	git -C collision-super diff --submodule=log >actual &&
+	printf "Submodule sm1 %s..%s:\n  > child\n" \
+		"$(test_oid submodule_commit1_abbrev)" \
+		"$(git -C collision-super/sm1 rev-parse --short "$commit2")" >expected &&
+	test_cmp expected actual
+'
+
 # Test non-UTF-8 encoding in case iconv is available.
 if test_have_prereq ICONV
 then

base-commit: 50fe5cc63f9cd6e89b87a2c9ccf96a444f4cfdb7

-- 
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