mercurial/scmwindows.py

debugcommands: prevent using `is False`

I was touching this code in a future patch and marmoute warned about usage of
`is False` here.

Quoting marmoute:

```
"is False" is going to check if the object you have the very same object in
memory than the one Python allocated for False (in practice 0)
This will "mostly work" on cpython because of implementation details, but
is semantically wrong and can start breaking unexpectedly
```

Differential Revision: https://phab.mercurial-scm.org/D10014

from __future__ import absolute_import

import os

from . import (
    encoding,
    pycompat,
    util,
    win32,
)

try:
    import _winreg as winreg  # pytype: disable=import-error

    winreg.CloseKey
except ImportError:
    # py2 only
    import winreg  # pytype: disable=import-error

# MS-DOS 'more' is the only pager available by default on Windows.
fallbackpager = b'more'


def systemrcpath():
    '''return default os-specific hgrc search path'''
    rcpath = []
    filename = win32.executablepath()
    # Use mercurial.ini found in directory with hg.exe
    progrc = os.path.join(os.path.dirname(filename), b'mercurial.ini')
    rcpath.append(progrc)

    def _processdir(progrcd):
        if os.path.isdir(progrcd):
            for f, kind in sorted(util.listdir(progrcd)):
                if f.endswith(b'.rc'):
                    rcpath.append(os.path.join(progrcd, f))

    # Use hgrc.d found in directory with hg.exe
    _processdir(os.path.join(os.path.dirname(filename), b'hgrc.d'))

    # treat a PROGRAMDATA directory as equivalent to /etc/mercurial
    programdata = encoding.environ.get(b'PROGRAMDATA')
    if programdata:
        programdata = os.path.join(programdata, b'Mercurial')
        _processdir(os.path.join(programdata, b'hgrc.d'))

        ini = os.path.join(programdata, b'mercurial.ini')
        if os.path.isfile(ini):
            rcpath.append(ini)

        ini = os.path.join(programdata, b'hgrc')
        if os.path.isfile(ini):
            rcpath.append(ini)

    # next look for a system rcpath in the registry
    value = util.lookupreg(
        b'SOFTWARE\\Mercurial', None, winreg.HKEY_LOCAL_MACHINE
    )
    if value and isinstance(value, bytes):
        value = util.localpath(value)
        for p in value.split(pycompat.ospathsep):
            if p.lower().endswith(b'mercurial.ini'):
                rcpath.append(p)
            else:
                _processdir(p)
    return rcpath


def userrcpath():
    '''return os-specific hgrc search path to the user dir'''
    home = _legacy_expanduser(b'~')
    path = [os.path.join(home, b'mercurial.ini'), os.path.join(home, b'.hgrc')]
    userprofile = encoding.environ.get(b'USERPROFILE')
    if userprofile and userprofile != home:
        path.append(os.path.join(userprofile, b'mercurial.ini'))
        path.append(os.path.join(userprofile, b'.hgrc'))
    return path


def _legacy_expanduser(path):
    """Expand ~ and ~user constructs in the pre 3.8 style"""

    # Python 3.8+ changed the expansion of '~' from HOME to USERPROFILE.  See
    # https://bugs.python.org/issue36264.  It also seems to capitalize the drive
    # letter, as though it was processed through os.path.realpath().
    if not path.startswith(b'~'):
        return path

    i, n = 1, len(path)
    while i < n and path[i] not in b'\\/':
        i += 1

    if b'HOME' in encoding.environ:
        userhome = encoding.environ[b'HOME']
    elif b'USERPROFILE' in encoding.environ:
        userhome = encoding.environ[b'USERPROFILE']
    elif b'HOMEPATH' not in encoding.environ:
        return path
    else:
        try:
            drive = encoding.environ[b'HOMEDRIVE']
        except KeyError:
            drive = b''
        userhome = os.path.join(drive, encoding.environ[b'HOMEPATH'])

    if i != 1:  # ~user
        userhome = os.path.join(os.path.dirname(userhome), path[1:i])

    return userhome + path[i:]


def termsize(ui):
    return win32.termsize()