subcmds/cherry_pick.py

# Copyright (C) 2010 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import re
import sys
from typing import Tuple

from command import Command
from error import GitError
from git_command import GitCommand
from repo_logging import RepoLogger


CHANGE_ID_RE = re.compile(r"^\s*Change-Id: I([0-9a-f]{40})\s*$")
logger = RepoLogger(__file__)


class CherryPick(Command):
    COMMON = True
    helpSummary = "Cherry-pick a change."
    helpUsage = """
%prog <sha1>
"""
    helpDescription = """
'%prog' cherry-picks a change from one branch to another.
The change id will be updated, and a reference to the old
change id will be added.
"""

    def ValidateOptions(self, opt, args):
        if len(args) != 1:
            self.Usage()

    def Execute(self, opt, args):
        reference = args[0]
        sha1, commit = self._ResolveReference(reference)
        old_msg = self._StripHeader(commit)

        p = GitCommand(
            None,
            ["cherry-pick", sha1],
            capture_stdout=True,
            capture_stderr=True,
            verify_command=True,
        )

        try:
            p.Wait()
        except GitError as e:
            logger.error(e)
            logger.warning(
                "NOTE: When committing (please see above) and editing the "
                "commit message, please remove the old Change-Id-line and "
                "add:\n%s",
                self._GetReference(sha1),
            )
            raise

        if p.stdout:
            print(p.stdout.strip(), file=sys.stdout)
        if p.stderr:
            print(p.stderr.strip(), file=sys.stderr)

        # The cherry-pick was applied correctly. We just need to edit
        # the commit message.
        new_msg = self._Reformat(old_msg, sha1)

        p = GitCommand(
            None,
            ["commit", "--amend", "-F", "-"],
            input=new_msg,
            capture_stdout=True,
            capture_stderr=True,
            verify_command=True,
        )
        try:
            p.Wait()
        except GitError:
            logger.error("error: Failed to update commit message")
            raise

    def _ResolveReference(self, reference: str) -> Tuple[str, str]:
        """Resolve a commit and read it through one cat-file batch request."""
        expression = f"{reference}^{{commit}}"
        p = GitCommand(
            None,
            ["cat-file", "--batch"],
            input=expression + "\n",
            capture_stdout=True,
            capture_stderr=True,
            verify_command=True,
        )
        try:
            p.Wait()
            header, separator, output = p.stdout.partition("\n")
            if not separator:
                raise ValueError("missing cat-file header")
            if header.endswith(" missing") or header.endswith(" ambiguous"):
                raise GitError(f"commit {reference} not found")

            parts = header.split(" ", 2)
            if len(parts) != 3 or parts[1] != "commit":
                raise ValueError(
                    f"unexpected object type {parts[1]!r}"
                    if len(parts) >= 2
                    else "invalid header"
                )
            sha1, _object_type, _size = parts

            if not output.endswith("\n"):
                raise ValueError("truncated cat-file object")

            commit = output[:-1]
        except (GitError, ValueError) as e:
            logger.error(
                "error: Failed to resolve or read commit %s", reference
            )
            if isinstance(e, GitError):
                raise
            raise GitError(str(e)) from e

        return sha1, commit

    def _IsChangeId(self, line):
        return CHANGE_ID_RE.match(line)

    def _GetReference(self, sha1):
        return "(cherry picked from commit %s)" % sha1

    def _StripHeader(self, commit_msg):
        lines = commit_msg.splitlines()
        return "\n".join(lines[lines.index("") + 1 :])

    def _Reformat(self, old_msg, sha1):
        new_msg = []

        for line in old_msg.splitlines():
            if not self._IsChangeId(line):
                new_msg.append(line)

        # Add a blank line between the message and the change id/reference.
        try:
            if new_msg[-1].strip() != "":
                new_msg.append("")
        except IndexError:
            pass

        new_msg.append(self._GetReference(sha1))
        return "\n".join(new_msg)