ref: check whether the target of the symref is a ref

Ideally, we want to the users use "git symbolic-ref" to create symrefs
instead of writing raw contents into the filesystem. However, "git
symbolic-ref" is strict with the refname but not strict with the
referent. For example, we can make the "referent" located at the
"$(gitdir)/logs/aaa" and manually write the content into this where we
can still successfully parse this symref by using "git rev-parse".

  $ git init repo && cd repo && git commit --allow-empty -mx
  $ git symbolic-ref refs/heads/test logs/aaa
  $ echo $(git rev-parse HEAD) > .git/logs/aaa
  $ git rev-parse test

We may need to add some restrictions for "referent" parameter when using
"git symbolic-ref" to create symrefs because ideally all the
nonpseudo-refs should be located under the "refs" directory and we may
tighten this in the future.

In order to tell the user we may tighten the above situation, create
a new fsck message "symrefTargetIsNotARef" to notify the user that this
may become an error in the future.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: shejialuo <shejialuo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/refs/files-backend.c b/refs/files-backend.c
index f4342e3f3e..c2b99fdf40 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -3513,6 +3513,7 @@ static int files_fsck_symref_target(struct fsck_options *o,
 				    struct fsck_ref_report *report,
 				    struct strbuf *referent)
 {
+	int is_referent_root;
 	char orig_last_byte;
 	size_t orig_len;
 	int ret = 0;
@@ -3521,8 +3522,17 @@ static int files_fsck_symref_target(struct fsck_options *o,
 	orig_last_byte = referent->buf[orig_len - 1];
 	strbuf_rtrim(referent);
 
-	if (!is_root_ref(referent->buf) &&
-	    check_refname_format(referent->buf, 0)) {
+	is_referent_root = is_root_ref(referent->buf);
+	if (!is_referent_root &&
+	    !starts_with(referent->buf, "refs/") &&
+	    !starts_with(referent->buf, "worktrees/")) {
+		ret = fsck_report_ref(o, report,
+				      FSCK_MSG_SYMREF_TARGET_IS_NOT_A_REF,
+				      "points to non-ref target '%s'", referent->buf);
+
+	}
+
+	if (!is_referent_root && check_refname_format(referent->buf, 0)) {
 		ret = fsck_report_ref(o, report,
 				      FSCK_MSG_BAD_REFERENT_NAME,
 				      "points to invalid refname '%s'", referent->buf);