push, fetch: error out for submodule entries not pointing to commits

The check_has_commit helper uses resolves a submodule entry to a
commit, when validating its existence. As a side effect this means
tolerates a submodule entry pointing to a tag, which is not a valid
submodule entry that git commands would know how to cope with.

Tighten the check to require an actual commit, not a tag pointing to a
commit.

Also improve the error handling when a submodule entry points to
non-commit (e.g., a blob) to error out instead of warning and
pretending the pointed to object doesn't exist.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 35 insertions, 8 deletions

diff --git a/submodule.c b/submodule.c
index 3cea8221e0..e0da55920d 100644
--- a/submodule.c
+++ b/submodule.c
@@ -767,19 +767,36 @@ static int append_oid_to_argv(const struct object_id *oid, void *data)
 	return 0;
 }
 
+struct has_commit_data {
+	int result;
+	const char *path;
+};
+
 static int check_has_commit(const struct object_id *oid, void *data)
 {
-	int *has_commit = data;
+	struct has_commit_data *cb = data;
 
-	if (!lookup_commit_reference(oid))
-		*has_commit = 0;
+	enum object_type type = sha1_object_info(oid->hash, NULL);
 
-	return 0;
+	switch (type) {
+	case OBJ_COMMIT:
+		return 0;
+	case OBJ_BAD:
+		/*
+		 * Object is missing or invalid. If invalid, an error message
+		 * has already been printed.
+		 */
+		cb->result = 0;
+		return 0;
+	default:
+		die(_("submodule entry '%s' (%s) is a %s, not a commit"),
+		    cb->path, oid_to_hex(oid), typename(type));
+	}
 }
 
 static int submodule_has_commits(const char *path, struct oid_array *commits)
 {
-	int has_commit = 1;
+	struct has_commit_data has_commit = { 1, path };
 
 	/*
 	 * Perform a cheap, but incorrect check for the existence of 'commits'.
@@ -795,7 +812,7 @@ static int submodule_has_commits(const char *path, struct oid_array *commits)
 
 	oid_array_for_each_unique(commits, check_has_commit, &has_commit);
 
-	if (has_commit) {
+	if (has_commit.result) {
 		/*
 		 * Even if the submodule is checked out and the commit is
 		 * present, make sure it exists in the submodule's object store
@@ -814,12 +831,12 @@ static int submodule_has_commits(const char *path, struct oid_array *commits)
 		cp.dir = path;
 
 		if (capture_command(&cp, &out, GIT_MAX_HEXSZ + 1) || out.len)
-			has_commit = 0;
+			has_commit.result = 0;
 
 		strbuf_release(&out);
 	}
 
-	return has_commit;
+	return has_commit.result;
 }
 
 static int submodule_needs_pushing(const char *path, struct oid_array *commits)
diff --git a/t/t5531-deep-submodule-push.sh b/t/t5531-deep-submodule-push.sh
index 0f84a53146..39cb2c1c34 100755
--- a/t/t5531-deep-submodule-push.sh
+++ b/t/t5531-deep-submodule-push.sh
@@ -298,6 +298,16 @@ test_expect_success 'push succeeds if submodule commit disabling recursion from
 	)
 '
 
+test_expect_success 'submodule entry pointing at a tag is error' '
+	git -C work/gar/bage tag -a test1 -m "tag" &&
+	tag=$(git -C work/gar/bage rev-parse test1^{tag}) &&
+	git -C work update-index --cacheinfo 160000 "$tag" gar/bage &&
+	git -C work commit -m "bad commit" &&
+	test_when_finished "git -C work reset --hard HEAD^" &&
+	test_must_fail git -C work push --recurse-submodules=on-demand ../pub.git master 2>err &&
+	test_i18ngrep "is a tag, not a commit" err
+'
+
 test_expect_success 'push fails if recurse submodules option passed as yes' '
 	(
 		cd work/gar/bage &&