Use a specific Exception type

[git-cache] / git_cache.py

diff --git a/git_cache.py b/git_cache.py
index 1ed26017ceb18f0831d8b5566068c6eb11fdcf7a..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"
@@ -78,14 +90,14 @@ def verify_ancestry(
         ancestor: RefOrRev,
         force: bool = False) -> None:
     if not force and not is_ancestor(repo, descendant, ancestor):
-        raise Exception('%s is not an ancestor of %s' % (ancestor, descendant))
+        raise GitCacheError(f'{ancestor} is not an ancestor of {descendant}')
 
 
 def _read_fetch_log(repo: Repo) -> Iterator[_LogEntry]:
     filename = _log_filename(repo)
     if not os.path.exists(filename):
         return
-    with open(filename, 'r') as f:
+    with open(filename, 'r', encoding='utf-8') as f:
         for line in f:
             _, _, rev, ref = line.strip().split(maxsplit=3)
             yield _LogEntry(ref, rev)
@@ -107,10 +119,11 @@ def _log_fetch(repo: Repo, ref: Ref, rev: Rev, force: bool = False) -> None:
             verify_ancestry(repo, rev, prev_rev)
     filename = _log_filename(repo)
     os.makedirs(os.path.dirname(filename), exist_ok=True)
-    with open(filename, 'a') as f:
-        f.write('%s %s %s %s\n' %
-                (time.strftime('%Y-%m%d-%H:%M:%S%z'),
-                 ('FORCEDFETCH' if force else 'fetch'), rev, ref))
+    with open(filename, 'a', encoding='utf-8') as f:
+        f.write(
+            f'{time.strftime("%Y-%m%d-%H:%M:%S%z")} '
+            f'{"FORCEDFETCH" if force else "fetch"} {rev} {ref}\n'
+        )
 
 
 def _show_force_warning() -> None:
@@ -150,7 +163,7 @@ def _show_force_warning() -> None:
 ''', end='', file=sys.stderr)
 
     for i in range(warn_time, 0, -1):
-        msg = '* %-70s *' % ("Continuing in %d seconds..." % i)
+        msg = f'* {f"Continuing in {i} seconds...":-70s} *'
         print(msg, file=sys.stderr)
         time.sleep(1)
     print('*' * 74, file=sys.stderr)
@@ -167,7 +180,7 @@ def _git_fetch(
         force: bool = False) -> None:
     subprocess.run(['git', '-C', cachedir, 'fetch'] +
                    (['--force'] if force else []) +
-                   [repo, '%s:%s' % (ref, ref)], check=True)
+                   [repo, f'{ref}:{ref}'], check=True)
 
 
 def fetch(repo: Repo, ref: Ref, force: bool = False) -> Tuple[Path, Rev]:
@@ -188,7 +201,7 @@ def fetch(repo: Repo, ref: Ref, force: bool = False) -> Tuple[Path, Rev]:
     logging.debug('Fetching ref "%s" from %s', ref, repo)
     _git_fetch(cachedir, repo, ref, force=force)
 
-    with open(os.path.join(cachedir, 'refs', 'heads', ref)) as rev_file:
+    with open(os.path.join(cachedir, 'refs', 'heads', ref), encoding='utf-8') as rev_file:
         rev = Rev(rev_file.read(999).strip())
     verify_ancestry(repo, ref, rev, force=force)
     _log_fetch(repo, ref, rev, force=force)
@@ -244,7 +257,8 @@ def _main() -> None:
     args = parser.parse_args()
 
     if args.rev is None:
-        print('{1} {0}'.format(*fetch(args.repo, args.ref, force=args.force)))
+        cachedir, rev = fetch(args.repo, args.ref, force=args.force)
+        print(f'{rev} {cachedir}')
     else:
         print(
             ensure_rev_available(