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lethe/lethe/lethe.py

305 lines
9.7 KiB

#!/usr/bin/env python3
"""
Git snapshotting tool
"""
from typing import Sequence, Union, Optional
import subprocess
import tempfile
import datetime
import argparse
from itertools import chain
def _run(command: Union[str, Sequence[str]], **kwargs) -> str:
"""
Wrapper for `subprocess.run()`:
- Accepts args as either a list of strings or space-delimited string
- Captures and returns stdout
Args:
command: A list of strings or a space-delimited string
**kwargs: Passed to `subprocess.run()`
Returns:
Captured stdout
"""
args: Sequence[str]
if isinstance(command, str):
args = command.split()
else:
args = command
result = subprocess.run(args, stdout=subprocess.PIPE, **kwargs)
return result.stdout.decode().strip()
def get_latest_commit(short: bool = True, cwd: Optional[str] = None) -> str:
"""
Get the most recent commit's hash.
This includes non-lethe commits.
"""
fmt = 'h' if short else 'H'
return _run(f'git log --all -1 --format=%{fmt}', cwd=cwd)
def shorten_hash(sha: str, cwd: Optional[str] = None) -> str:
"""
Get the short version of a hash
"""
return _run(f'git rev-parse --short {sha}', cwd=cwd)
def get_root(cwd: Optional[str] = None) -> str:
"""
Get the root directory of a git repository
"""
root = _run('git rev-parse --show-toplevel', cwd=cwd)
if not root:
raise Exception('Must be run from inside git repository!')
return root
def get_obj(ref: str, cwd: Optional[str] = None) -> str:
"""
Transform a ref into its corresponding hash using git-rev-parse
"""
sha = _run('git rev-parse --quiet --verify'.split() + [ref], cwd=cwd)
return sha
def get_commit(ref: str, cwd: Optional[str] = None) -> str:
"""
Transform a ref to a commit into its corresponding hash using git-rev-parse
"""
return get_obj(ref, cwd=cwd)
def get_tree(ref: str, cwd: Optional[str] = None) -> str:
"""
Take a ref to a commit, and return the hash of the tree it points to
"""
return get_obj(ref + ':', cwd=cwd)
def commit_tree(tree: str,
parents: Sequence[str],
message: Optional[str] = None,
cwd: Optional[str] = None,
) -> str:
"""
Create a commit pointing to the given tree, with the specified parent commits and message.
Return the hash of the created commit.
"""
if message is None:
message = 'snapshot ' + str(datetime.datetime.now())
pargs = list(chain.from_iterable(('-p', p) for p in parents))
commit = _run(['git', 'commit-tree', tree, *pargs, '-m', message], cwd=cwd) # Create commit
return commit
def update_ref(target_ref: str,
target_commit: str,
old_commit: Optional[str] = None,
*,
message: str = 'new snapshot',
cwd: Optional[str] = None,
) -> str:
"""
Update `target_ref` to point to `target_commit`, optionally verifying that
it points `old_commit` before the update.
Returns the resulting ref.
"""
cmd = ['git', 'update-ref', '-m', message, target_ref, target_commit]
if old_commit is not None:
cmd.append(old_commit)
result_ref = _run(cmd, cwd=cwd)
return result_ref
def push_ref(remote: str = 'origin',
target_ref: str = 'refs/lethe/LATEST',
remote_ref: Optional[str] = None,
*,
cwd: Optional[str] = None,
) -> str:
"""
Push `target_ref` to `remote` as `remote_ref`.
By default, `remote_ref` will be the same as `target_ref`.
Args:
remote: git remote to push to (default 'origin')
target_ref: ref to push (default 'refs/lethe/LATEST')
remote_ref: ref to push to (default same as `target_ref`)
cwd: Repository directory. Default is current working directory.
Returns:
git command stdout
"""
if remote_ref is None:
remote_ref = target_ref
return _run(['git', 'push', '--force', remote, target_ref + ':' + remote_ref], cwd=cwd)
def fetch_ref(remote: str = 'origin',
remote_ref: str = 'refs/lethe/LATEST',
target_ref: Optional[str] = None,
*,
cwd: Optional[str] = None,
) -> str:
"""
Fetch `remote_ref` from `remote` as `target_ref`.
By default, `target_ref` will be the same as `remote_ref`.
Args:
remote: git remote to push to (default 'origin')
remote_ref: ref to fetch from (default 'refs/lethe/LATEST')
target_ref: ref to fetch to (default same as `remote_ref`)
cwd: Repository directory. Default is current working directory.
Returns:
git command stdout
"""
if target_ref is None:
target_ref = remote_ref
return _run(['git', 'fetch', '--force', remote, remote_ref + ':' + target_ref], cwd=cwd)
def deref_symref(ref: str,
*,
cwd: Optional[str] = None,
) -> str:
"""
Dereference a symbolic ref
"""
return _run(['git', 'symbolic-ref', '--quiet', ref], cwd=cwd)
def find_merge_base(commits: Sequence[str],
*,
cwd: Optional[str] = None,
) -> str:
"""
Find the "best common ancestor" commit.
Args:
commits: Collection of commits to find the best common ancestor for
cwd: Repository directory. Default is current working directory.
Returns:
Hash of the best common ancestor commit
"""
if len(commits) == 0:
raise Exception('Called find_merge_base with no commits!')
if len(commits) == 1:
return commits[0]
base = _run(['git', 'merge-base', *commits], cwd=cwd)
return base
def snap_tree(*, cwd: Optional[str] = None) -> str:
"""
Create a new tree, consisting of all non-ignored files in the repository.
Return the hash of the tree.
"""
with tempfile.TemporaryDirectory() as tmp_dir:
env = {'GIT_INDEX_FILE': tmp_dir + '/git-snapshot-index'}
# TODO: Maybe need cwd=get_root(cwd) here?
_run('git add --all', env=env, cwd=cwd)
tree = _run('git write-tree', env=env, cwd=cwd)
return tree
def snap_ref(parent_refs: Sequence[str],
target_refs: Sequence[str],
message: Optional[str] = None,
*,
cwd: Optional[str] = None,
) -> str:
"""
`message` is used as the commit message.
"""
new_tree = snap_tree(cwd=cwd)
parent_commits = [c for c in [get_commit(p, cwd=cwd) for p in parent_refs] if c]
old_commits = [get_commit(t, cwd=cwd) for t in target_refs]
commit = commit_tree(new_tree, set(parent_commits), message, cwd=cwd)
for target_ref, old_commit in zip(target_refs, old_commits):
# update ref to point to commit, or create new ref
old_or_none = old_commit if old_commit else None
update_ref(target_ref, commit, old_commit=old_or_none, cwd=cwd)
return commit
def snap(parent_refs: Optional[Sequence[str]] = None,
target_refs: Optional[Sequence[str]] = None,
message: Optional[str] = None,
*,
cwd: Optional[str] = None,
) -> str:
"""
Create a new commit, containing all non-ignored files.
Args:
parent_refs: Refs in this list are set as parents of the new commit.
If any symbolic refs are included, the underlying refs they point
to are also added to `parent_refs`. Defaults to `['HEAD']`.
target_refs: Refs in this list will be updated to point to the new commit.
Default is
- 'refs/lethe/LATEST', and
- 'refs/lethe/path/to/ref/LATEST' and
'refs/lethe/path/to/ref/snap_2020-12-20_18.21.14.281876'
for each parent_ref of the form 'refs/path/to/ref'.
Symbolic refs are dereferenced, so a parent_ref of 'master'
will results in the creation/overwrite of
'refs/lethe/heads/master/LATEST'
Note that 'refs/lethe/LATEST' must be specified explicitly if the default
is overridden
message: The commit message. Default is a simple note containing the current
date/time.
cwd: Path to the repository. Default is the current working directory.
Returns:
The hash for the new commit.
"""
if parent_refs is None:
parent_refs = ['HEAD']
else:
parent_refs = list(parent_refs)
parent_refs += [r for r in [deref_symref(s, cwd=cwd) for s in parent_refs] if r]
date_str = str(datetime.datetime.now())
date_ref = date_str.replace(' ', '_').replace(':', '.')
if target_refs is None:
target_refs = ['refs/lethe/LATEST']
for pp in parent_refs:
if not pp.startswith('refs/'):
continue
target_base = 'refs/lethe/' + pp[len('refs/'):]
target_refs += [target_base + '/LATEST',
target_base + '/' + date_ref]
# Auto-migrate old commits to work with the new scheme
old_base_commit = get_commit(target_base, cwd=cwd)
if old_base_commit:
print(f'Migrating {target_base} to new naming scheme ({target_base}/LEGACY)...')
print(f'You may also want to delete refs/lethe/HEAD with `git update-ref -d refs/lethe/HEAD`')
_run('git update-ref -d ' + target_base)
update_ref(target_base + '/LEGACY', old_base_commit,
message='last commit using old refs/lethe/branchname approach')
if message is None:
message = 'snapshot ' + date_str
commit = snap_ref(parent_refs, target_refs, message=message, cwd=cwd)
return commit