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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2019 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Maps LLVM git SHAs to synthetic revision numbers and back.
Revision numbers are all of the form '(branch_name, r1234)'. As a shorthand,
r1234 is parsed as '(main, 1234)'.
"""
from __future__ import print_function
import argparse
import re
import subprocess
import sys
import typing as t
MAIN_BRANCH = 'main'
# Note that after base_llvm_sha, we reach The Wild West(TM) of commits.
# So reasonable input that could break us includes:
#
# Revert foo
#
# This reverts foo, which had the commit message:
#
# bar
# llvm-svn: 375505
#
# While saddening, this is something we should probably try to handle
# reasonably.
base_llvm_revision = 375505
base_llvm_sha = '186155b89c2d2a2f62337081e3ca15f676c9434b'
# Represents an LLVM git checkout:
# - |dir| is the directory of the LLVM checkout
# - |remote| is the name of the LLVM remote. Generally it's "origin".
LLVMConfig = t.NamedTuple('LLVMConfig', (('remote', str), ('dir', str)))
class Rev(t.NamedTuple('Rev', (('branch', str), ('number', int)))):
"""Represents a LLVM 'revision', a shorthand identifies a LLVM commit."""
@staticmethod
def parse(rev: str) -> 'Rev':
"""Parses a Rev from the given string.
Raises a ValueError on a failed parse.
"""
# Revs are parsed into (${branch_name}, r${commits_since_base_commit})
# pairs.
#
# We support r${commits_since_base_commit} as shorthand for
# (main, r${commits_since_base_commit}).
if rev.startswith('r'):
branch_name = MAIN_BRANCH
rev_string = rev[1:]
else:
match = re.match(r'\((.+), r(\d+)\)', rev)
if not match:
raise ValueError("%r isn't a valid revision" % rev)
branch_name, rev_string = match.groups()
return Rev(branch=branch_name, number=int(rev_string))
def __str__(self) -> str:
branch_name, number = self
if branch_name == MAIN_BRANCH:
return 'r%d' % number
return '(%s, r%d)' % (branch_name, number)
def is_git_sha(xs: str) -> bool:
"""Returns whether the given string looks like a valid git commit SHA."""
return len(xs) > 6 and len(xs) <= 40 and all(
x.isdigit() or 'a' <= x.lower() <= 'f' for x in xs)
def check_output(command: t.List[str], cwd: str) -> str:
"""Shorthand for subprocess.check_output. Auto-decodes any stdout."""
result = subprocess.run(
command,
cwd=cwd,
check=True,
stdin=subprocess.DEVNULL,
stdout=subprocess.PIPE,
encoding='utf-8',
)
return result.stdout
def translate_prebase_sha_to_rev_number(llvm_config: LLVMConfig,
sha: str) -> int:
"""Translates a sha to a revision number (e.g., "llvm-svn: 1234").
This function assumes that the given SHA is an ancestor of |base_llvm_sha|.
"""
commit_message = check_output(
['git', 'log', '-n1', '--format=%B', sha],
cwd=llvm_config.dir,
)
last_line = commit_message.strip().splitlines()[-1]
svn_match = re.match(r'^llvm-svn: (\d+)$', last_line)
if not svn_match:
raise ValueError(
f"No llvm-svn line found for {sha}, which... shouldn't happen?")
return int(svn_match.group(1))
def translate_sha_to_rev(llvm_config: LLVMConfig, sha_or_ref: str) -> Rev:
"""Translates a sha or git ref to a Rev."""
if is_git_sha(sha_or_ref):
sha = sha_or_ref
else:
sha = check_output(
['git', 'rev-parse', sha_or_ref],
cwd=llvm_config.dir,
)
sha = sha.strip()
merge_base = check_output(
['git', 'merge-base', base_llvm_sha, sha],
cwd=llvm_config.dir,
)
merge_base = merge_base.strip()
if merge_base == base_llvm_sha:
result = check_output(
[
'git',
'rev-list',
'--count',
'--first-parent',
f'{base_llvm_sha}..{sha}',
],
cwd=llvm_config.dir,
)
count = int(result.strip())
return Rev(branch=MAIN_BRANCH, number=count + base_llvm_revision)
# Otherwise, either:
# - |merge_base| is |sha| (we have a guaranteed llvm-svn number on |sha|)
# - |merge_base| is neither (we have a guaranteed llvm-svn number on
# |merge_base|, but not |sha|)
merge_base_number = translate_prebase_sha_to_rev_number(
llvm_config, merge_base)
if merge_base == sha:
return Rev(branch=MAIN_BRANCH, number=merge_base_number)
distance_from_base = check_output(
[
'git',
'rev-list',
'--count',
'--first-parent',
f'{merge_base}..{sha}',
],
cwd=llvm_config.dir,
)
revision_number = merge_base_number + int(distance_from_base.strip())
branches_containing = check_output(
['git', 'branch', '-r', '--contains', sha],
cwd=llvm_config.dir,
)
candidates = []
prefix = llvm_config.remote + '/'
for branch in branches_containing.splitlines():
branch = branch.strip()
if branch.startswith(prefix):
candidates.append(branch[len(prefix):])
if not candidates:
raise ValueError(
f'No viable branches found from {llvm_config.remote} with {sha}')
if len(candidates) != 1:
raise ValueError(
f'Ambiguity: multiple branches from {llvm_config.remote} have {sha}: '
f'{sorted(candidates)}')
return Rev(branch=candidates[0], number=revision_number)
def parse_git_commit_messages(stream: t.Iterable[str],
separator: str) -> t.Iterable[t.Tuple[str, str]]:
"""Parses a stream of git log messages.
These are expected to be in the format:
40 character sha
commit
message
body
separator
40 character sha
commit
message
body
separator
"""
lines = iter(stream)
while True:
# Looks like a potential bug in pylint? crbug.com/1041148
# pylint: disable=stop-iteration-return
sha = next(lines, None)
if sha is None:
return
sha = sha.strip()
assert is_git_sha(sha), f'Invalid git SHA: {sha}'
message = []
for line in lines:
if line.strip() == separator:
break
message.append(line)
yield sha, ''.join(message)
def translate_prebase_rev_to_sha(llvm_config: LLVMConfig, rev: Rev) -> str:
"""Translates a Rev to a SHA.
This function assumes that the given rev refers to a commit that's an
ancestor of |base_llvm_sha|.
"""
# Because reverts may include reverted commit messages, we can't just |-n1|
# and pick that.
separator = '>!' * 80
looking_for = f'llvm-svn: {rev.number}'
git_command = [
'git', 'log', '--grep', f'^{looking_for}$', f'--format=%H%n%B{separator}',
base_llvm_sha
]
subp = subprocess.Popen(
git_command,
cwd=llvm_config.dir,
stdin=subprocess.DEVNULL,
stdout=subprocess.PIPE,
encoding='utf-8',
)
with subp:
for sha, message in parse_git_commit_messages(subp.stdout, separator):
last_line = message.splitlines()[-1]
if last_line.strip() == looking_for:
subp.terminate()
return sha
if subp.returncode:
raise subprocess.CalledProcessError(subp.returncode, git_command)
raise ValueError(f'No commit with revision {rev} found')
def translate_rev_to_sha(llvm_config: LLVMConfig, rev: Rev) -> str:
"""Translates a Rev to a SHA.
Raises a ValueError if the given Rev doesn't exist in the given config.
"""
branch, number = rev
if branch == MAIN_BRANCH:
if number < base_llvm_revision:
return translate_prebase_rev_to_sha(llvm_config, rev)
base_sha = base_llvm_sha
base_revision_number = base_llvm_revision
else:
base_sha = check_output(
['git', 'merge-base', base_llvm_sha, f'{llvm_config.remote}/{branch}'],
cwd=llvm_config.dir,
)
base_sha = base_sha.strip()
if base_sha == base_llvm_sha:
base_revision_number = base_llvm_revision
else:
base_revision_number = translate_prebase_sha_to_rev_number(
llvm_config, base_sha)
# Alternatively, we could |git log --format=%H|, but git is *super* fast
# about rev walking/counting locally compared to long |log|s, so we walk back
# twice.
head = check_output(
['git', 'rev-parse', f'{llvm_config.remote}/{branch}'],
cwd=llvm_config.dir,
)
branch_head_sha = head.strip()
commit_number = number - base_revision_number
revs_between_str = check_output(
[
'git',
'rev-list',
'--count',
'--first-parent',
f'{base_sha}..{branch_head_sha}',
],
cwd=llvm_config.dir,
)
revs_between = int(revs_between_str.strip())
commits_behind_head = revs_between - commit_number
if commits_behind_head < 0:
raise ValueError(
f'Revision {rev} is past {llvm_config.remote}/{branch}. Try updating '
'your tree?')
result = check_output(
['git', 'rev-parse', f'{branch_head_sha}~{commits_behind_head}'],
cwd=llvm_config.dir,
)
return result.strip()
def find_root_llvm_dir(root_dir: str = '.') -> str:
"""Finds the root of an LLVM directory starting at |root_dir|.
Raises a subprocess.CalledProcessError if no git directory is found.
"""
result = check_output(
['git', 'rev-parse', '--show-toplevel'],
cwd=root_dir,
)
return result.strip()
def main(argv: t.List[str]) -> None:
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument(
'--llvm_dir',
help='LLVM directory to consult for git history, etc. Autodetected '
'if cwd is inside of an LLVM tree')
parser.add_argument(
'--upstream',
default='origin',
help="LLVM upstream's remote name. Defaults to %(default)s.")
sha_or_rev = parser.add_mutually_exclusive_group(required=True)
sha_or_rev.add_argument(
'--sha', help='A git SHA (or ref) to convert to a rev')
sha_or_rev.add_argument('--rev', help='A rev to convert into a sha')
opts = parser.parse_args(argv)
llvm_dir = opts.llvm_dir
if llvm_dir is None:
try:
llvm_dir = find_root_llvm_dir()
except subprocess.CalledProcessError:
parser.error("Couldn't autodetect an LLVM tree; please use --llvm_dir")
config = LLVMConfig(
remote=opts.upstream,
dir=opts.llvm_dir or find_root_llvm_dir(),
)
if opts.sha:
rev = translate_sha_to_rev(config, opts.sha)
print(rev)
else:
sha = translate_rev_to_sha(config, Rev.parse(opts.rev))
print(sha)
if __name__ == '__main__':
main(sys.argv[1:])