[PATCH v2 1/2] submodule: use the submodule repository to abbreviate commits

["Srujith A Poojary via GitGitGadget" <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.

As the expected abbreviation depends on the hash algorithm used,
the test uses the test_oid mechanism to switch the expectation
between SHA-1 and SHA-256 repositories.

Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
---
 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
-- 
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