mercurial/txnutil.py

color: add a 'ui.color' option to control color behavior

This new option control whether or not color will be used. It mirror the behavior
of '--color'. I usually avoid adding new option to '[ui]' as the section is
already filled with many option. However, I feel like 'color' is central enough
to deserves a spot in this '[ui]' section.

For now the option is not documented so it is still marked as experimental. Once
it get documented and official, we should be able to deprecate the color
extensions.

There is more cleanup to do before that documentation is written, but we need
this option early to made them. Having that option will allow for more cleanup
of the initialisation process and proper separation between color
configuration.

# txnutil.py - transaction related utilities
#
#  Copyright FUJIWARA Katsunori <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

from . import (
    encoding,
)

def mayhavepending(root):
    '''return whether 'root' may have pending changes, which are
    visible to this process.
    '''
    return root == encoding.environ.get('HG_PENDING')

def trypending(root, vfs, filename, **kwargs):
    '''Open  file to be read according to HG_PENDING environment variable

    This opens '.pending' of specified 'filename' only when HG_PENDING
    is equal to 'root'.

    This returns '(fp, is_pending_opened)' tuple.
    '''
    if mayhavepending(root):
        try:
            return (vfs('%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)