contrib/simplemerge

util: use ~ as a suffix for a temp file in the same directory as a source file

Tools like Buck have patterns to ignore the creation of files (in the working
copy) that match certain patterns:

https://github.com/facebook/buck/blob/39278a4f0701c5239eae148968dc1ed4cc8661f7/src/com/facebook/buck/cli/Main.java#L259-L299

When Buck sees a new source file (as reported by Watchman), it has to invalidate
a number of caches associated with the directory that contains the file.
Using a standard suffix, such as `~`, would make it easier for Buck and others
to filter out these types of file creation events.

The other uses of `tempfile.mkstemp()` in Hg do not appear to be problematic
because they (generally speaking) do not specify the `dir` parameter, so the
new file is created in the system-appropriate temp directory, which is outside
the working copy.

Test Plan:
`make tests`

Differential Revision: https://phab.mercurial-scm.org/D468

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

import getopt
import sys

import hgdemandimport
hgdemandimport.enable()

from mercurial.i18n import _
from mercurial import (
    error,
    fancyopts,
    simplemerge,
    ui as uimod,
    util,
)

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

usage = _('''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():
    sys.stdout.write(usage)
    sys.stdout.write('\noptions:\n')

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

class filebackedctx(object):
    """simplemerge requires context-like objects"""
    def __init__(self, path):
        self._path = path

    def decodeddata(self):
        with open(self._path, "rb") as f:
            return f.read()

    def flags(self):
        return ''

    def path(self):
        return self._path

    def write(self, data, flags):
        assert not flags
        with open(self._path, "w") as f:
            f.write(data)

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

    opts = {}
    try:
        args = fancyopts.fancyopts(sys.argv[1:], options, opts)
    except getopt.GetoptError as e:
        raise ParseError(e)
    if opts['help']:
        showhelp()
        sys.exit(0)
    if len(args) != 3:
            raise ParseError(_('wrong number of arguments'))
    local, base, other = args
    sys.exit(simplemerge.simplemerge(uimod.ui.load(),
                                     filebackedctx(local),
                                     filebackedctx(base),
                                     filebackedctx(other),
                                     filtereddata=True,
                                     **opts))
except ParseError as e:
    sys.stdout.write("%s: %s\n" % (sys.argv[0], e))
    showhelp()
    sys.exit(1)
except error.Abort as e:
    sys.stderr.write("abort: %s\n" % e)
    sys.exit(255)
except KeyboardInterrupt:
    sys.exit(255)