Use a specific Exception type

[git-cache] / git_cache.py

diff --git a/git_cache.py b/git_cache.py
index c7bcdd215e2cf52bda04483ecb267d0b72ade596..8171b48f3a06e8b4921bbcce5dcb028980c4d8d0 100644 (file)
--- a/git_cache.py
+++ b/git_cache.py
@@ -1,3 +1,10 @@
+# git-cache: Cache git content locally
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, version 3.
+
+
 # It would be nice if we could share the nix git cache, but as of the
 # time of writing it is transitioning from gitv2 (deprecated) to gitv3
 # (not ready yet), and trying to straddle them both is too far into nix
@@ -17,6 +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"
@@ -78,7 +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]: