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#!/usr/bin/env python
#
# ======- git-llvm - LLVM Git Help Integration ---------*- python -*--========#
#
#                     The LLVM Compiler Infrastructure
#
# This file is distributed under the University of Illinois Open Source
# License. See LICENSE.TXT for details.
#
# ==------------------------------------------------------------------------==#

"""
git-llvm integration
====================

This file provides integration for git.
"""

from __future__ import print_function
import argparse
import collections
import contextlib
import errno
import os
import re
import subprocess
import sys
import tempfile
import time
assert sys.version_info >= (2, 7)


# It's *almost* a straightforward mapping from the monorepo to svn...
GIT_TO_SVN_DIR = {
    d: (d + '/trunk')
    for d in [
        'clang-tools-extra',
        'compiler-rt',
        'dragonegg',
        'klee',
        'libclc',
        'libcxx',
        'libcxxabi',
        'lld',
        'lldb',
        'llvm',
        'polly',
    ]
}
GIT_TO_SVN_DIR.update({'clang': 'cfe/trunk'})

VERBOSE = False
QUIET = False


def eprint(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)


def log(*args, **kwargs):
    if QUIET:
        return
    print(*args, **kwargs)


def log_verbose(*args, **kwargs):
    if not VERBOSE:
        return
    print(*args, **kwargs)


def die(msg):
    eprint(msg)
    sys.exit(1)


def first_dirname(d):
    while True:
        (head, tail) = os.path.split(d)
        if not head or head == '/':
            return tail
        d = head


def shell(cmd, strip=True, cwd=None, stdin=None, die_on_failure=True):
    log_verbose('Running: %s' % ' '.join(cmd))

    start = time.time()
    p = subprocess.Popen(cmd, cwd=cwd, stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE, stdin=subprocess.PIPE)
    stdout, stderr = p.communicate(input=stdin)
    elapsed = time.time() - start

    log_verbose('Command took %0.1fs' % elapsed)

    if p.returncode == 0:
        if stderr:
            eprint('`%s` printed to stderr:' % ' '.join(cmd))
            eprint(stderr.rstrip())
        if strip:
            stdout = stdout.rstrip('\r\n')
        return stdout
    err_msg = '`%s` returned %s' % (' '.join(cmd), p.returncode)
    eprint(err_msg)
    if stderr:
        eprint(stderr.rstrip())
    if die_on_failure:
        sys.exit(2)
    raise RuntimeError(err_msg)


def git(*cmd, **kwargs):
    return shell(['git'] + list(cmd), kwargs.get('strip', True))


def svn(cwd, *cmd, **kwargs):
    # TODO: Better way to do default arg when we have *cmd?
    return shell(['svn'] + list(cmd), cwd=cwd, stdin=kwargs.get('stdin', None))


def get_default_rev_range():
    # Get the branch tracked by the current branch, as set by
    # git branch --set-upstream-to  See http://serverfault.com/a/352236/38694.
    cur_branch = git('rev-parse', '--symbolic-full-name', 'HEAD')
    upstream_branch = git('for-each-ref', '--format=%(upstream:short)',
                          cur_branch)
    if not upstream_branch:
        upstream_branch = 'origin/master'

    # Get the newest common ancestor between HEAD and our upstream branch.
    upstream_rev = git('merge-base', 'HEAD', upstream_branch)
    return '%s..' % upstream_rev


def get_revs_to_push(rev_range):
    if not rev_range:
        rev_range = get_default_rev_range()
    # Use git show rather than some plumbing command to figure out which revs
    # are in rev_range because it handles single revs (HEAD^) and ranges
    # (foo..bar) like we want.
    revs = git('show', '--reverse', '--quiet',
               '--pretty=%h', rev_range).splitlines()
    if not revs:
        die('Nothing to push: No revs in range %s.' % rev_range)
    return revs


def clean_and_update_svn(svn_repo):
    svn(svn_repo, 'revert', '-R', '.')

    # Unfortunately it appears there's no svn equivalent for git clean, so we
    # have to do it ourselves.
    for line in svn(svn_repo, 'status').split('\n'):
        if not line.startswith('?'):
            continue
        filename = line[1:].strip()
        os.remove(os.path.join(svn_repo, filename))

    svn(svn_repo, 'update', *list(GIT_TO_SVN_DIR.values()))


def svn_init(svn_root):
    if not os.path.exists(svn_root):
        log('Creating svn staging directory: (%s)' % (svn_root))
        os.makedirs(svn_root)
        log('This is a one-time initialization, please be patient for a few'
            ' minutes...')
        svn(svn_root, 'checkout', '--depth=immediates',
            'https://llvm.org/svn/llvm-project/', '.')
        svn(svn_root, 'update', *list(GIT_TO_SVN_DIR.values()))
        log("svn staging area ready in '%s'" % svn_root)
    if not os.path.isdir(svn_root):
        die("Can't initialize svn staging dir (%s)" % svn_root)


def svn_push_one_rev(svn_repo, rev, dry_run):
    files = git('diff-tree', '--no-commit-id', '--name-only', '-r',
                rev).split('\n')
    subrepos = {first_dirname(f) for f in files}
    if not subrepos:
        raise RuntimeError('Empty diff for rev %s?' % rev)

    status = svn(svn_repo, 'status')
    if status:
        die("Can't push git rev %s because svn status is not empty:\n%s" %
            (rev, status))

    for sr in subrepos:
        diff = git('show', '--binary', rev, '--', sr, strip=False)
        svn_sr_path = os.path.join(svn_repo, GIT_TO_SVN_DIR[sr])
        # git is the only thing that can handle its own patches...
        log_verbose('Apply patch: %s' % diff)
        try:
            shell(['git', 'apply', '-p2', '-'], cwd=svn_sr_path, stdin=diff,
                  die_on_failure=False)
        except RuntimeError as e:
            eprint("Patch doesn't apply: maybe you should try `git pull -r` "
                   "first?")
            sys.exit(2)

    status_lines = svn(svn_repo, 'status').split('\n')

    for l in (l for l in status_lines if l.startswith('?')):
        svn(svn_repo, 'add', l[1:].strip())
    for l in (l for l in status_lines if l.startswith('!')):
        svn(svn_repo, 'remove', l[1:].strip())

    # Now we're ready to commit.
    commit_msg = git('show', '--pretty=%B', '--quiet', rev)
    if not dry_run:
        log(svn(svn_repo, 'commit', '-m', commit_msg, '--force-interactive'))
        log('Committed %s to svn.' % rev)
    else:
        log("Would have committed %s to svn, if this weren't a dry run." % rev)


def cmd_push(args):
    '''Push changes back to SVN: this is extracted from Justin Lebar's script
    available here: https://github.com/jlebar/llvm-repo-tools/

    Note: a current limitation is that git does not track file rename, so they
    will show up in SVN as delete+add.
    '''
    # Get the git root
    git_root = git('rev-parse', '--show-toplevel')
    if not os.path.isdir(git_root):
        die("Can't find git root dir")

    # Push from the root of the git repo
    os.chdir(git_root)

    # We need a staging area for SVN, let's hide it in the .git directory.
    dot_git_dir = git('rev-parse', '--git-common-dir')
    svn_root = os.path.join(dot_git_dir, 'llvm-upstream-svn')
    svn_init(svn_root)

    rev_range = args.rev_range
    dry_run = args.dry_run
    revs = get_revs_to_push(rev_range)
    log('Pushing %d commit%s:\n%s' %
        (len(revs), 's' if len(revs) != 1
         else '', '\n'.join('  ' + git('show', '--oneline', '--quiet', c)
                            for c in revs)))
    for r in revs:
        clean_and_update_svn(svn_root)
        svn_push_one_rev(svn_root, r, dry_run)


if __name__ == '__main__':
    argv = sys.argv[1:]
    p = argparse.ArgumentParser(
        prog='git llvm', formatter_class=argparse.RawDescriptionHelpFormatter,
        description=__doc__)
    subcommands = p.add_subparsers(title='subcommands',
                                   description='valid subcommands',
                                   help='additional help')
    verbosity_group = p.add_mutually_exclusive_group()
    verbosity_group.add_argument('-q', '--quiet', action='store_true',
                                 help='print less information')
    verbosity_group.add_argument('-v', '--verbose', action='store_true',
                                 help='print more information')

    parser_push = subcommands.add_parser(
        'push', description=cmd_push.__doc__,
        help='push changes back to the LLVM SVN repository')
    parser_push.add_argument(
        '-n',
        '--dry-run',
        dest='dry_run',
        action='store_true',
        help='Do everything other than commit to svn.  Leaves junk in the svn '
        'repo, so probably will not work well if you try to commit more '
        'than one rev.')
    parser_push.add_argument(
        'rev_range',
        metavar='GIT_REVS',
        type=str,
        nargs='?',
        help="revs to push (default: everything not in the branch's "
        'upstream, or not in origin/master if the branch lacks '
        'an explicit upstream)')
    parser_push.set_defaults(func=cmd_push)
    args = p.parse_args(argv)
    VERBOSE = args.verbose
    QUIET = args.quiet

    # Dispatch to the right subcommand
    args.func(args)