contrib/simplemerge

resolve: use the `parentchange` context manager to apply merge action

In an ideal world, we would not have to do that. However, we are miles away from
being ready to not have to do it.

So we add this context manager alongside a long comment. This will help use to
get to the point were have two distinct API with strict rules about when to call
them.

Differential Revision: https://phab.mercurial-scm.org/D11074

#!/usr/bin/env python3
from __future__ import absolute_import

import getopt
import sys

import hgdemandimport

hgdemandimport.enable()

from mercurial.i18n import _
from mercurial import (
    context,
    error,
    fancyopts,
    pycompat,
    simplemerge,
    ui as uimod,
)
from mercurial.utils import procutil, stringutil

options = [
    (b'L', b'label', [], _(b'labels to use on conflict markers')),
    (b'a', b'text', None, _(b'treat all files as text')),
    (b'p', b'print', None, _(b'print results instead of overwriting LOCAL')),
    (b'', b'no-minimal', None, _(b'no effect (DEPRECATED)')),
    (b'h', b'help', None, _(b'display help and exit')),
    (b'q', b'quiet', None, _(b'suppress output')),
]

usage = _(
    b'''simplemerge [OPTS] LOCAL BASE OTHER

    Simple three-way file merge utility with a minimal feature set.

    Apply to LOCAL the changes necessary to go from BASE to OTHER.

    By default, LOCAL is overwritten with the results of this operation.
'''
)


class ParseError(Exception):
    """Exception raised on errors in parsing the command line."""


def showhelp():
    procutil.stdout.write(usage)
    procutil.stdout.write(b'\noptions:\n')

    out_opts = []
    for shortopt, longopt, default, desc in options:
        out_opts.append(
            (
                b'%2s%s'
                % (
                    shortopt and b'-%s' % shortopt,
                    longopt and b' --%s' % longopt,
                ),
                b'%s' % desc,
            )
        )
    opts_len = max([len(opt[0]) for opt in out_opts])
    for first, second in out_opts:
        procutil.stdout.write(b' %-*s  %s\n' % (opts_len, first, second))


try:
    for fp in (sys.stdin, procutil.stdout, sys.stderr):
        procutil.setbinary(fp)

    opts = {}
    try:
        bargv = [a.encode('utf8') for a in sys.argv[1:]]
        args = fancyopts.fancyopts(bargv, options, opts)
    except getopt.GetoptError as e:
        raise ParseError(e)
    if opts[b'help']:
        showhelp()
        sys.exit(0)
    if len(args) != 3:
        raise ParseError(_(b'wrong number of arguments').decode('utf8'))
    local, base, other = args
    sys.exit(
        simplemerge.simplemerge(
            uimod.ui.load(),
            context.arbitraryfilectx(local),
            context.arbitraryfilectx(base),
            context.arbitraryfilectx(other),
            **pycompat.strkwargs(opts)
        )
    )
except ParseError as e:
    e = stringutil.forcebytestr(e)
    procutil.stdout.write(b"%s: %s\n" % (sys.argv[0].encode('utf8'), e))
    showhelp()
    sys.exit(1)
except error.Abort as e:
    procutil.stderr.write(b"abort: %s\n" % e)
    sys.exit(255)
except KeyboardInterrupt:
    sys.exit(255)