refs: split off reading loose ref data in separate function

This prepares for handling FETCH_HEAD (which is not a regular ref)
separately from the ref backend.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs/files-backend.c

@@ -360,7 +360,6 @@ static int files_read_raw_ref(struct ref_store *ref_store,
 	struct strbuf sb_path = STRBUF_INIT;
 	const char *path;
 	const char *buf;
-	const char *p;
 	struct stat st;
 	int fd;
 	int ret = -1;
@@ -465,29 +464,8 @@ stat_ref:
 	close(fd);
 	strbuf_rtrim(&sb_contents);
 	buf = sb_contents.buf;
-	if (skip_prefix(buf, "ref:", &buf)) {
-		while (isspace(*buf))
-			buf++;
 
-		strbuf_reset(referent);
-		strbuf_addstr(referent, buf);
-		*type |= REF_ISSYMREF;
-		ret = 0;
-		goto out;
-	}
-
-	/*
-	 * Please note that FETCH_HEAD has additional
-	 * data after the sha.
-	 */
-	if (parse_oid_hex(buf, oid, &p) ||
-	    (*p != '\0' && !isspace(*p))) {
-		*type |= REF_ISBROKEN;
-		errno = EINVAL;
-		goto out;
-	}
-
-	ret = 0;
+	ret = parse_loose_ref_contents(buf, oid, referent, type);
 
 out:
 	save_errno = errno;
@@ -497,6 +475,32 @@ out:
 	return ret;
 }
 
+int parse_loose_ref_contents(const char *buf, struct object_id *oid,
+			     struct strbuf *referent, unsigned int *type)
+{
+	const char *p;
+	if (skip_prefix(buf, "ref:", &buf)) {
+		while (isspace(*buf))
+			buf++;
+
+		strbuf_reset(referent);
+		strbuf_addstr(referent, buf);
+		*type |= REF_ISSYMREF;
+		return 0;
+	}
+
+	/*
+	 * FETCH_HEAD has additional data after the sha.
+	 */
+	if (parse_oid_hex(buf, oid, &p) ||
+	    (*p != '\0' && !isspace(*p))) {
+		*type |= REF_ISBROKEN;
+		errno = EINVAL;
+		return -1;
+	}
+	return 0;
+}
+
 static void unlock_ref(struct ref_lock *lock)
 {
 	rollback_lock_file(&lock->lk);

refs/refs-internal.h

@@ -674,6 +674,12 @@ struct ref_store {
 	const struct ref_storage_be *be;
 };
 
+/*
+ * Parse contents of a loose ref file.
+ */
+int parse_loose_ref_contents(const char *buf, struct object_id *oid,
+			     struct strbuf *referent, unsigned int *type);
+
 /*
  * Fill in the generic part of refs and add it to our collection of
  * reference stores.