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66a78bc217
At the moment, the revert ordering from this tool is unspecified (though it happens to be in `git log` order, so newest reverts come first). From the standpoint of tooling and users, this seems to be the opposite of what we want by default: tools and users will generally try to apply these reverts as cherry-picks. If two reverts in the list are close enough to each other, if the reverts get applied out of order, we'll get a merge conflict. Rather than having `reverse`s for all tools (and mental reverses for manual users), just guarantee an oldest-first output ordering for this function. Differential Revision: https://reviews.llvm.org/D106838
265 lines
8.5 KiB
Python
Executable File
265 lines
8.5 KiB
Python
Executable File
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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#===----------------------------------------------------------------------===##
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#
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# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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# See https://llvm.org/LICENSE.txt for license information.
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# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#
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#===----------------------------------------------------------------------===##
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"""Checks for reverts of commits across a given git commit.
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To clarify the meaning of 'across' with an example, if we had the following
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commit history (where `a -> b` notes that `b` is a direct child of `a`):
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123abc -> 223abc -> 323abc -> 423abc -> 523abc
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And where 423abc is a revert of 223abc, this revert is considered to be 'across'
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323abc. More generally, a revert A of a parent commit B is considered to be
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'across' a commit C if C is a parent of A and B is a parent of C.
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Please note that revert detection in general is really difficult, since merge
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conflicts/etc always introduce _some_ amount of fuzziness. This script just
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uses a bundle of heuristics, and is bound to ignore / incorrectly flag some
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reverts. The hope is that it'll easily catch the vast majority (>90%) of them,
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though.
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This is designed to be used in one of two ways: an import in Python, or run
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directly from a shell. If you want to import this, the `find_reverts`
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function is the thing to look at. If you'd rather use this from a shell, have a
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usage example:
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```
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./revert_checker.py c47f97169 origin/main origin/release/12.x
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```
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This checks for all reverts from the tip of origin/main to c47f97169, which are
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across the latter. It then does the same for origin/release/12.x to c47f97169.
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Duplicate reverts discovered when walking both roots (origin/main and
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origin/release/12.x) are deduplicated in output.
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"""
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import argparse
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import collections
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import logging
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import re
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import subprocess
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import sys
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from typing import Generator, List, NamedTuple, Iterable
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assert sys.version_info >= (3, 6), 'Only Python 3.6+ is supported.'
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# People are creative with their reverts, and heuristics are a bit difficult.
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# Like 90% of of reverts have "This reverts commit ${full_sha}".
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# Some lack that entirely, while others have many of them specified in ad-hoc
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# ways, while others use short SHAs and whatever.
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#
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# The 90% case is trivial to handle (and 100% free + automatic). The extra 10%
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# starts involving human intervention, which is probably not worth it for now.
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def _try_parse_reverts_from_commit_message(commit_message: str) -> List[str]:
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if not commit_message:
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return []
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results = re.findall(r'This reverts commit ([a-f0-9]{40})\b', commit_message)
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first_line = commit_message.splitlines()[0]
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initial_revert = re.match(r'Revert ([a-f0-9]{6,}) "', first_line)
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if initial_revert:
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results.append(initial_revert.group(1))
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return results
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def _stream_stdout(command: List[str]) -> Generator[str, None, None]:
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with subprocess.Popen(
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command, stdout=subprocess.PIPE, encoding='utf-8', errors='replace') as p:
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assert p.stdout is not None # for mypy's happiness.
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yield from p.stdout
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def _resolve_sha(git_dir: str, sha: str) -> str:
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if len(sha) == 40:
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return sha
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return subprocess.check_output(
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['git', '-C', git_dir, 'rev-parse', sha],
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encoding='utf-8',
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stderr=subprocess.DEVNULL,
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).strip()
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_LogEntry = NamedTuple('_LogEntry', [
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('sha', str),
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('commit_message', str),
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])
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def _log_stream(git_dir: str, root_sha: str,
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end_at_sha: str) -> Iterable[_LogEntry]:
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sep = 50 * '<>'
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log_command = [
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'git',
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'-C',
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git_dir,
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'log',
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'^' + end_at_sha,
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root_sha,
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'--format=' + sep + '%n%H%n%B%n',
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]
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stdout_stream = iter(_stream_stdout(log_command))
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# Find the next separator line. If there's nothing to log, it may not exist.
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# It might not be the first line if git feels complainy.
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found_commit_header = False
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for line in stdout_stream:
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if line.rstrip() == sep:
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found_commit_header = True
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break
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while found_commit_header:
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sha = next(stdout_stream, None)
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assert sha is not None, 'git died?'
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sha = sha.rstrip()
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commit_message = []
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found_commit_header = False
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for line in stdout_stream:
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line = line.rstrip()
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if line.rstrip() == sep:
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found_commit_header = True
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break
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commit_message.append(line)
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yield _LogEntry(sha, '\n'.join(commit_message).rstrip())
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def _shas_between(git_dir: str, base_ref: str, head_ref: str) -> Iterable[str]:
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rev_list = [
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'git',
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'-C',
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git_dir,
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'rev-list',
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'--first-parent',
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f'{base_ref}..{head_ref}',
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]
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return (x.strip() for x in _stream_stdout(rev_list))
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def _rev_parse(git_dir: str, ref: str) -> str:
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return subprocess.check_output(
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['git', '-C', git_dir, 'rev-parse', ref],
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encoding='utf-8',
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).strip()
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Revert = NamedTuple('Revert', [
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('sha', str),
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('reverted_sha', str),
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])
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def _find_common_parent_commit(git_dir: str, ref_a: str, ref_b: str) -> str:
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"""Finds the closest common parent commit between `ref_a` and `ref_b`."""
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return subprocess.check_output(
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['git', '-C', git_dir, 'merge-base', ref_a, ref_b],
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encoding='utf-8',
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).strip()
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def find_reverts(git_dir: str, across_ref: str, root: str) -> List[Revert]:
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"""Finds reverts across `across_ref` in `git_dir`, starting from `root`.
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These reverts are returned in order of oldest reverts first.
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"""
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across_sha = _rev_parse(git_dir, across_ref)
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root_sha = _rev_parse(git_dir, root)
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common_ancestor = _find_common_parent_commit(git_dir, across_sha, root_sha)
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if common_ancestor != across_sha:
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raise ValueError(f"{across_sha} isn't an ancestor of {root_sha} "
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'(common ancestor: {common_ancestor})')
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intermediate_commits = set(_shas_between(git_dir, across_sha, root_sha))
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assert across_sha not in intermediate_commits
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logging.debug('%d commits appear between %s and %s',
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len(intermediate_commits), across_sha, root_sha)
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all_reverts = []
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for sha, commit_message in _log_stream(git_dir, root_sha, across_sha):
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reverts = _try_parse_reverts_from_commit_message(commit_message)
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if not reverts:
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continue
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resolved_reverts = sorted(set(_resolve_sha(git_dir, x) for x in reverts))
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for reverted_sha in resolved_reverts:
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if reverted_sha in intermediate_commits:
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logging.debug('Commit %s reverts %s, which happened after %s', sha,
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reverted_sha, across_sha)
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continue
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try:
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object_type = subprocess.check_output(
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['git', '-C', git_dir, 'cat-file', '-t', reverted_sha],
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encoding='utf-8',
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stderr=subprocess.DEVNULL,
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).strip()
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except subprocess.CalledProcessError:
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logging.warning(
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'Failed to resolve reverted object %s (claimed to be reverted '
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'by sha %s)', reverted_sha, sha)
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continue
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if object_type == 'commit':
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all_reverts.append(Revert(sha, reverted_sha))
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continue
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logging.error("%s claims to revert %s -- which isn't a commit -- %s", sha,
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object_type, reverted_sha)
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# Since `all_reverts` contains reverts in log order (e.g., newer comes before
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# older), we need to reverse this to keep with our guarantee of older =
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# earlier in the result.
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all_reverts.reverse()
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return all_reverts
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def _main() -> None:
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parser = argparse.ArgumentParser(
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description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
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parser.add_argument(
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'base_ref', help='Git ref or sha to check for reverts around.')
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parser.add_argument(
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'-C', '--git_dir', default='.', help='Git directory to use.')
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parser.add_argument(
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'root', nargs='+', help='Root(s) to search for commits from.')
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parser.add_argument('--debug', action='store_true')
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opts = parser.parse_args()
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logging.basicConfig(
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format='%(asctime)s: %(levelname)s: %(filename)s:%(lineno)d: %(message)s',
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level=logging.DEBUG if opts.debug else logging.INFO,
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)
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# `root`s can have related history, so we want to filter duplicate commits
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# out. The overwhelmingly common case is also to have one root, and it's way
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# easier to reason about output that comes in an order that's meaningful to
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# git.
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seen_reverts = set()
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all_reverts = []
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for root in opts.root:
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for revert in find_reverts(opts.git_dir, opts.base_ref, root):
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if revert not in seen_reverts:
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seen_reverts.add(revert)
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all_reverts.append(revert)
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for revert in all_reverts:
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print(f'{revert.sha} claims to revert {revert.reverted_sha}')
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if __name__ == '__main__':
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_main()
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