refs API: make refs_rename_ref_available() static

Move the refs_rename_ref_available() function into
"refs/files-backend.c". It is file-backend specific.

This function was added in 5fe7d825da (refs.c: pass a list of names
to skip to is_refname_available, 2014-05-01) as rename_ref_available()
and was only ever used in this one file-backend specific codepath. So
let's move it there.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -1372,25 +1372,6 @@ const char *find_descendant_ref(const char *dirname,
 	return NULL;
 }
 
-int refs_rename_ref_available(struct ref_store *refs,
-			      const char *old_refname,
-			      const char *new_refname)
-{
-	struct string_list skip = STRING_LIST_INIT_NODUP;
-	struct strbuf err = STRBUF_INIT;
-	int ok;
-
-	string_list_insert(&skip, old_refname);
-	ok = !refs_verify_refname_available(refs, new_refname,
-					    NULL, &skip, &err);
-	if (!ok)
-		error("%s", err.buf);
-
-	string_list_clear(&skip, 0);
-	strbuf_release(&err);
-	return ok;
-}
-
 int refs_head_ref(struct ref_store *refs, each_ref_fn fn, void *cb_data)
 {
 	struct object_id oid;

refs/files-backend.c

@@ -1363,6 +1363,35 @@ static int commit_ref_update(struct files_ref_store *refs,
 			     const struct object_id *oid, const char *logmsg,
 			     struct strbuf *err);
 
+/*
+ * Check whether an attempt to rename old_refname to new_refname would
+ * cause a D/F conflict with any existing reference (other than
+ * possibly old_refname). If there would be a conflict, emit an error
+ * message and return false; otherwise, return true.
+ *
+ * Note that this function is not safe against all races with other
+ * processes (though rename_ref() catches some races that might get by
+ * this check).
+ */
+static int refs_rename_ref_available(struct ref_store *refs,
+			      const char *old_refname,
+			      const char *new_refname)
+{
+	struct string_list skip = STRING_LIST_INIT_NODUP;
+	struct strbuf err = STRBUF_INIT;
+	int ok;
+
+	string_list_insert(&skip, old_refname);
+	ok = !refs_verify_refname_available(refs, new_refname,
+					    NULL, &skip, &err);
+	if (!ok)
+		error("%s", err.buf);
+
+	string_list_clear(&skip, 0);
+	strbuf_release(&err);
+	return ok;
+}
+
 static int files_copy_or_rename_ref(struct ref_store *ref_store,
 			    const char *oldrefname, const char *newrefname,
 			    const char *logmsg, int copy)

refs/refs-internal.h

@@ -228,20 +228,6 @@ const char *find_descendant_ref(const char *dirname,
 				const struct string_list *extras,
 				const struct string_list *skip);
 
-/*
- * Check whether an attempt to rename old_refname to new_refname would
- * cause a D/F conflict with any existing reference (other than
- * possibly old_refname). If there would be a conflict, emit an error
- * message and return false; otherwise, return true.
- *
- * Note that this function is not safe against all races with other
- * processes (though rename_ref() catches some races that might get by
- * this check).
- */
-int refs_rename_ref_available(struct ref_store *refs,
-			      const char *old_refname,
-			      const char *new_refname);
-
 /* We allow "recursive" symbolic refs. Only within reason, though */
 #define SYMREF_MAXDEPTH 5