feat(git): added update_refs method that validate refs before settings a value

vcsserver/remote/git_remote.py

@@ -1101,6 +1101,14 b' class GitRemote(RemoteBase):'
             repo.references.create(key, value, force=True)
 
     @reraise_safe_exceptions
+    def update_refs(self, wire, key, value):
+        repo_init = self._factory.repo_libgit2(wire)
+        with repo_init as repo:
+            if key not in repo.references:
+                raise ValueError(f'Reference {key} not found in the repository')
+            repo.references.create(key, value, force=True)
+
+    @reraise_safe_exceptions
     def create_branch(self, wire, branch_name, commit_id, force=False):
         repo_init = self._factory.repo_libgit2(wire)
         with repo_init as repo: