Revert submodule commits accidentally included in the most recent commit

revert_submodule_updates.py

import os
import pathlib
import re
import shlex
import subprocess
import sys


def main():
    if git("status", "--porcelain"):
        exit(error=True, msg="Working directory is not clean")

    submodule_commits = find_submodule_commits()
    if not submodule_commits:
        exit(error=False)

    for submodule, commit in submodule_commits.items():
        git("checkout", commit, cwd=f"third_party/{submodule}")

    git("add", "third_party")
    git("commit", "--amend", "--no-edit")


THIRD_PARTY_PATTERN = re.compile(r"diff --git ([ab]/third_party/(?P<submodule>[^/]+)){2}")
OLD_COMMIT_PATTERN = re.compile(r"-Subproject commit (?P<commit>[\da-f]{40})")


def find_submodule_commits():
    diff = iter(git("diff", "HEAD~1").split("\n"))
    submodule_commits = {}
    for line in diff:
        match = THIRD_PARTY_PATTERN.match(line)
        if not match:
            continue

        submodule = match.group("submodule")

        for line in diff:
            match = OLD_COMMIT_PATTERN.match(line)
            if not match:
                continue

            commit = match.group("commit")
            submodule_commits[submodule] = commit
            break

    return submodule_commits


def git(*cmds, cwd=None) -> str:
    if cwd is None:
        cwd = pathlib.Path.cwd()
    else:
        cwd = pathlib.Path(cwd)
        if not cwd.is_absolute():
            cwd = pathlib.Path.cwd() / cwd

    cmd = " ".join([shlex.quote(s) for s in ("git", *cmds)])
    print(f"${cmd}")
    return subprocess.check_output(cmd, shell=True, cwd=str(cwd)).decode()


def exit(*, error: bool, msg: str = ""):
    code, file = (1, sys.stderr) if error else (0, sys.stdout)
    if msg:
        print(msg, file=file)
    sys.exit(code)


if __name__ == "__main__":
    main()