X-Git-Url: http://git.scottworley.com/git-cache/blobdiff_plain/50685beba299ab4b601b6aabb013bb8398c8bfb0..d3b8a09dab31bd579466407aa9153219016eb45b:/git_cache.py

diff --git a/git_cache.py b/git_cache.py
index a34c329..8171b48 100644
--- a/git_cache.py
+++ b/git_cache.py
@@ -24,6 +24,11 @@ from typing import Iterator, NamedTuple, Optional, TypeVar, Tuple, Union
 
 import backoff
 
+
+class GitCacheError(Exception):
+    pass
+
+
 Path = str   # eg: "/home/user/.cache/git-cache/v1"
 Repo = str   # eg: "https://github.com/NixOS/nixpkgs.git"
 Ref = str    # eg: "master" or "v1.0.0"
@@ -85,7 +90,7 @@ def verify_ancestry(
         ancestor: RefOrRev,
         force: bool = False) -> None:
     if not force and not is_ancestor(repo, descendant, ancestor):
-        raise Exception(f'{ancestor} is not an ancestor of {descendant}')
+        raise GitCacheError(f'{ancestor} is not an ancestor of {descendant}')
 
 
 def _read_fetch_log(repo: Repo) -> Iterator[_LogEntry]: