+# 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
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"
'merge-base',
'--is-ancestor',
ancestor,
- descendant],
+ descendant.removeprefix('tag ')],
check=False)
return process.returncode == 0
def verify_ancestry(
repo: Repo,
descendant: RefOrRev,
- ancestor: RefOrRev) -> None:
- if not is_ancestor(repo, descendant, ancestor):
- raise Exception('%s is not an ancestor of %s' % (ancestor, descendant))
+ ancestor: RefOrRev,
+ force: bool = False) -> None:
+ if not force and not is_ancestor(repo, descendant, ancestor):
+ 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)
repo) if entry.ref == ref)
-def _log_fetch(repo: Repo, ref: Ref, rev: Rev) -> None:
- prev_rev = _previous_fetched_rev(repo, ref)
- if prev_rev is not None:
- verify_ancestry(repo, rev, prev_rev)
+def _log_fetch(repo: Repo, ref: Ref, rev: Rev, force: bool = False) -> None:
+ if not force:
+ prev_rev = _previous_fetched_rev(repo, ref)
+ if prev_rev is not 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 fetch %s %s\n' %
- (time.strftime('%Y-%m%d-%H:%M:%S%z'), 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:
+ print('''
+**************************************************************************
+* WARNING: git-cache INVOKED WITH --force! *
+* *
+* This mode allows previously-fetched refs to be overwritten to point to *
+* non-descendants -- commits that don't have the previous version of the *
+* the ref in their history! *
+* *
+* This should only be invoked by a human operator who knows what they're *
+* doing to correct a specific, known, problem. Care should be taken to *
+* prevent recurrence. *
+* *
+* Press ^C to abort. *
+* *
+''', end='', file=sys.stderr)
+ warn_time_override = os.environ.get('FORCE_WARNING_TIME', None)
+ warn_time: int
+ if warn_time_override is None:
+ warn_time = 15
+ else:
+ warn_time = int(warn_time_override)
+ print(
+ '''* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! *
+* !! WARNING DISPLAY TIME OVERRIDDEN !! *
+* !! !! *
+* !! This message is intended to be displayed long enough for a !! *
+* !! human operator to read it and have a chance to abort. An !! *
+* !! override for the delay time is provided FOR THE UNIT TESTS !! *
+* !! to avoid delaying software builds unnecessarily. This is !! *
+* !! INTENDED FOR USE IN UNIT TESTS ONLY; THIS MESSAGE SHOULD !! *
+* !! NEVER BE SEEN OUTSIDE BUILD LOGS! !! *
+* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! *
+* *
+''', end='', file=sys.stderr)
+
+ for i in range(warn_time, 0, -1):
+ msg = f'* {f"Continuing in {i} seconds...":-70s} *'
+ print(msg, file=sys.stderr)
+ time.sleep(1)
+ print('*' * 74, file=sys.stderr)
@backoff.on_exception(
backoff.expo,
subprocess.CalledProcessError,
max_time=lambda: int(os.environ.get('BACKOFF_MAX_TIME', '30')))
-def _git_fetch(cachedir: Path, repo: Repo, ref: Ref) -> None:
- # We don't use --force here because we want to abort and freak out if forced
- # updates are happening.
- subprocess.run(['git', '-C', cachedir, 'fetch', repo,
- '%s:%s' % (ref, ref)], check=True)
-
-
-def fetch(repo: Repo, ref: Ref) -> Tuple[Path, Rev]:
+def _git_fetch(
+ cachedir: Path,
+ repo: Repo,
+ ref: Ref,
+ force: bool = False) -> None:
+ refargs = (['tag', ref.removeprefix('tag ')]
+ if ref.startswith('tag ')
+ else [f'{ref}:{ref}'])
+ subprocess.run(['git', '-C', cachedir, 'fetch'] +
+ (['--force'] if force else []) +
+ [repo] + refargs, check=True)
+
+
+def fetch(repo: Repo, ref: Ref, force: bool = False) -> Tuple[Path, Rev]:
+ if force:
+ _show_force_warning()
cachedir = git_cachedir(repo)
if not os.path.exists(cachedir):
logging.debug("Initializing git repo")
- subprocess.run(['git', 'init', '--bare', cachedir],
- check=True, stdout=sys.stderr)
+ subprocess.run(['git',
+ '-c',
+ 'init.defaultBranch=git-cache--no-default-branch',
+ 'init',
+ '--bare',
+ cachedir],
+ check=True,
+ stdout=sys.stderr)
logging.debug('Fetching ref "%s" from %s', ref, repo)
- _git_fetch(cachedir, repo, ref)
+ _git_fetch(cachedir, repo, ref, force=force)
- with open(os.path.join(cachedir, 'refs', 'heads', ref)) as rev_file:
+ rev_path = (['tags', ref.removeprefix('tag ')]
+ if ref.startswith('tag ')
+ else ['heads', ref])
+ with open(os.path.join(cachedir, 'refs', *rev_path), encoding='utf-8') as rev_file:
rev = Rev(rev_file.read(999).strip())
- verify_ancestry(repo, ref, rev)
- _log_fetch(repo, ref, rev)
+ verify_ancestry(repo, ref, rev, force=force)
+ _log_fetch(repo, ref, rev, force=force)
return cachedir, rev
-def ensure_rev_available(repo: Repo, ref: Ref, rev: Rev) -> Path:
+def ensure_rev_available(
+ repo: Repo,
+ ref: Ref,
+ rev: Rev,
+ force: bool = False) -> Path:
cachedir = git_cachedir(repo)
if os.path.exists(cachedir) and is_ancestor(repo, ref, rev):
return cachedir
logging.debug(
'We do not have rev %s. We will fetch ref "%s" and hope it appears.',
rev, ref)
- fetch(repo, ref)
+ fetch(repo, ref, force=force)
logging.debug('Verifying that fetch retrieved rev %s', rev)
subprocess.run(['git', '-C', cachedir, 'cat-file', '-e', rev], check=True)
- verify_ancestry(repo, ref, rev)
+ verify_ancestry(repo, ref, rev, force=force)
return cachedir
parser = argparse.ArgumentParser(
description='Cache remote git repositories locally.',
epilog='example usage: git-cache https://github.com/NixOS/nixpkgs.git master')
+ parser.add_argument(
+ '--force',
+ action='store_true',
+ help='Recover from a force-push in the remote repo')
parser.add_argument(
'repo',
metavar='Repo',
args = parser.parse_args()
if args.rev is None:
- print('{1} {0}'.format(*fetch(args.repo, args.ref)))
+ cachedir, rev = fetch(args.repo, args.ref, force=args.force)
+ print(f'{rev} {cachedir}')
else:
- print(ensure_rev_available(args.repo, args.ref, args.rev))
+ print(
+ ensure_rev_available(
+ args.repo,
+ args.ref,
+ args.rev,
+ force=args.force))
projects / git-cache / blobdiff