fetch set_head: fix non-mirror remotes in bare repositories

Commit Message

Bence Ferdinandy Jan. 12, 2025, 4:51 p.m. UTC

In b1b713f722 (fetch set_head: handle mirrored bare repositories,
2024-11-22) it was implicitly assumed that all remotes will be mirrors
in a bare repository, thus fetching a non-mirrored remote could lead to
HEAD pointing to a non-existent reference. Make sure we only overwrite
HEAD if we are in a bare repository and fetching from a mirror.
Otherwise, proceed as normally, and create
refs/remotes/<nonmirrorremote>/HEAD instead.

Signed-off-by: Bence Ferdinandy <[e-mail]>
Reported-by: Christian Hesse <[e-mail]>
---
 builtin/fetch.c   | 15 ++++++++-------
 t/t5505-remote.sh | 10 ++++++++++
 t/t5510-fetch.sh  | 13 +++++++++++++
 3 files changed, 31 insertions(+), 7 deletions(-)


base-commit: fbe8d3079d4a96aeb4e4529cc93cc0043b759a05

Patch

diff --git a/builtin/fetch.c b/builtin/fetch.c
index fe2b26c74a..625d45be8b 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1618,9 +1618,9 @@  static void report_set_head(const char *remote, const char *head_name,
 }
 
 static int set_head(const struct ref *remote_refs, int follow_remote_head,
-		const char *no_warn_branch)
+		const char *no_warn_branch, int mirror)
 {
-	int result = 0, create_only, is_bare, was_detached;
+	int result = 0, create_only, baremirror, was_detached;
 	struct strbuf b_head = STRBUF_INIT, b_remote_head = STRBUF_INIT,
 		      b_local_head = STRBUF_INIT;
 	const char *remote = gtransport->remote->name;
@@ -1655,9 +1655,9 @@  static int set_head(const struct ref *remote_refs, int follow_remote_head,
 
 	if (!head_name)
 		goto cleanup;
-	is_bare = is_bare_repository();
-	create_only = follow_remote_head == FOLLOW_REMOTE_ALWAYS ? 0 : !is_bare;
-	if (is_bare) {
+	baremirror = is_bare_repository() && mirror;
+	create_only = follow_remote_head == FOLLOW_REMOTE_ALWAYS ? 0 : !baremirror;
+	if (baremirror) {
 		strbuf_addstr(&b_head, "HEAD");
 		strbuf_addf(&b_remote_head, "refs/heads/%s", head_name);
 	} else {
@@ -1665,7 +1665,7 @@  static int set_head(const struct ref *remote_refs, int follow_remote_head,
 		strbuf_addf(&b_remote_head, "refs/remotes/%s/%s", remote, head_name);
 	}
 		/* make sure it's valid */
-	if (!is_bare && !refs_ref_exists(refs, b_remote_head.buf)) {
+	if (!baremirror && !refs_ref_exists(refs, b_remote_head.buf)) {
 		result = 1;
 		goto cleanup;
 	}
@@ -1925,7 +1925,8 @@  static int do_fetch(struct transport *transport,
 		}
 	}
 	if (set_head(remote_refs, transport->remote->follow_remote_head,
-		transport->remote->no_warn_branch))
+		transport->remote->no_warn_branch,
+		transport->remote->mirror))
 		;
 		/*
 		 * Way too many cases where this can go wrong
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index 519f7973e3..c75cfe968f 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -589,6 +589,16 @@  test_expect_success 'add --mirror setting HEAD' '
 	)
 '
 
+test_expect_success 'non-mirror fetch does not interfere with mirror' '
+	mkdir headnotmain &&
+	(
+		cd headnotmain &&
+		git init --bare -b notmain &&
+		git remote add -f other ../two &&
+		test "$(git symbolic-ref HEAD)" = "refs/heads/notmain"
+	)
+'
+
 test_expect_success 'add --mirror=fetch' '
 	mkdir mirror-fetch &&
 	git init -b main mirror-fetch/parent &&
diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index 2d9587059f..cfa63ae086 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -84,6 +84,19 @@  test_expect_success "fetch test remote HEAD" '
 	branch=$(git rev-parse refs/remotes/origin/main) &&
 	test "z$head" = "z$branch"'
 
+test_expect_success "fetch test remote HEAD in bare repository" '
+	cd "$D" &&
+	git init --bare barerepo &&
+	cd barerepo &&
+	git remote add upstream ../two &&
+	git fetch upstream &&
+	git rev-parse --verify refs/remotes/upstream/HEAD &&
+	git rev-parse --verify refs/remotes/upstream/main &&
+	head=$(git rev-parse refs/remotes/upstream/HEAD) &&
+	branch=$(git rev-parse refs/remotes/upstream/main) &&
+	test "z$head" = "z$branch"'
+
+
 test_expect_success "fetch test remote HEAD change" '
 	cd "$D" &&
 	cd two &&