| | 1 | # It would be nice if we could share the nix git cache, but as of the |
| | 2 | # time of writing it is transitioning from gitv2 (deprecated) to gitv3 |
| | 3 | # (not ready yet), and trying to straddle them both is too far into nix |
| | 4 | # implementation details for my comfort. So we re-implement here half of |
| | 5 | # nix's builtins.fetchGit. :( |
| | 6 | |
| | 7 | import hashlib |
| | 8 | import logging |
| | 9 | import os |
| | 10 | import subprocess |
| | 11 | import sys |
| | 12 | |
| | 13 | from typing import Tuple |
| | 14 | |
| | 15 | Path = str # eg: "/home/user/.cache/git-cache/v1" |
| | 16 | Repo = str # eg: "https://github.com/NixOS/nixpkgs.git" |
| | 17 | Ref = str # eg: "master" or "v1.0.0" |
| | 18 | Rev = str # eg: "53a27350551844e1ed1a9257690294767389ef0d" |
| | 19 | |
| | 20 | |
| | 21 | def git_cachedir(repo: Repo) -> Path: |
| | 22 | # Use xdg module when it's less painful to have as a dependency |
| | 23 | XDG_CACHE_HOME = Path( |
| | 24 | os.environ.get('XDG_CACHE_HOME', os.path.expanduser('~/.cache'))) |
| | 25 | |
| | 26 | return Path(os.path.join( |
| | 27 | XDG_CACHE_HOME, |
| | 28 | 'git-cache/v1', |
| | 29 | hashlib.sha256(repo.encode()).hexdigest())) |
| | 30 | |
| | 31 | |
| | 32 | def verify_ancestry(repo: Repo, ref: Ref, rev: Rev) -> None: |
| | 33 | cachedir = git_cachedir(repo) |
| | 34 | logging.debug('Verifying rev %s is an ancestor of ref "%s"', rev, ref) |
| | 35 | subprocess.run(['git', '-C', cachedir, 'merge-base', '--is-ancestor', |
| | 36 | rev, ref], check=True) |
| | 37 | |
| | 38 | |
| | 39 | def fetch(repo: Repo, ref: Ref) -> Tuple[Path, Rev]: |
| | 40 | cachedir = git_cachedir(repo) |
| | 41 | if not os.path.exists(cachedir): |
| | 42 | logging.debug("Initializing git repo") |
| | 43 | subprocess.run(['git', 'init', '--bare', cachedir], check=True) |
| | 44 | |
| | 45 | logging.debug('Fetching ref "%s" from %s', ref, repo) |
| | 46 | # We don't use --force here because we want to abort and freak out if forced |
| | 47 | # updates are happening. |
| | 48 | subprocess.run(['git', '-C', cachedir, 'fetch', repo, |
| | 49 | '%s:%s' % (ref, ref)], check=True) |
| | 50 | |
| | 51 | with open(os.path.join(cachedir, 'refs', 'heads', ref)) as rev_file: |
| | 52 | rev = Rev(rev_file.read(999).strip()) |
| | 53 | verify_ancestry(repo, ref, rev) |
| | 54 | |
| | 55 | return cachedir, rev |
| | 56 | |
| | 57 | |
| | 58 | def ensure_rev_available(repo: Repo, ref: Ref, rev: Rev) -> Path: |
| | 59 | cachedir = git_cachedir(repo) |
| | 60 | if os.path.exists(cachedir): |
| | 61 | logging.debug('Checking if we already have rev %s', rev) |
| | 62 | process = subprocess.run( |
| | 63 | ['git', '-C', cachedir, 'cat-file', '-e', rev], check=False) |
| | 64 | if process.returncode == 0: |
| | 65 | logging.debug('We already have rev %s', rev) |
| | 66 | verify_ancestry(repo, ref, rev) |
| | 67 | return cachedir |
| | 68 | if process.returncode != 1: |
| | 69 | raise Exception( |
| | 70 | 'Could not test for presence of rev %s. Is cache dir "%s" messed up?' % |
| | 71 | (rev, cachedir)) |
| | 72 | |
| | 73 | logging.debug( |
| | 74 | 'We do not have rev %s. We will fetch ref "%s" and hope it appears.', |
| | 75 | rev, ref) |
| | 76 | fetch(repo, ref) |
| | 77 | logging.debug('Verifying that fetch retrieved rev %s', rev) |
| | 78 | subprocess.run(['git', '-C', cachedir, 'cat-file', '-e', rev], check=True) |
| | 79 | |
| | 80 | return cachedir |
| | 81 | |
| | 82 | |
| | 83 | def _main() -> None: |
| | 84 | if len(sys.argv) == 3: |
| | 85 | print('{1} {0}'.format(*fetch(Repo(sys.argv[1]), Ref(sys.argv[2])))) |
| | 86 | elif len(sys.argv) == 4: |
| | 87 | print(ensure_rev_available( |
| | 88 | Repo(sys.argv[1]), Ref(sys.argv[2]), Rev(sys.argv[3]))) |
| | 89 | else: |
| | 90 | usage = '''usage: git-cache repo ref [rev] |
| | 91 | example: git-cache https://github.com/NixOS/nixpkgs.git master''' |
| | 92 | print(usage, file=sys.stderr) |
| | 93 | sys.exit(1) |
projects / git-cache / blame_incremental