view mercurial/txnutil.py @ 39069:4c4825db29e1

shortest: don't include nullid in disambigution revset

As noted by Yuya in the review of D4118, the fact that the nodetree
always contains the nullid is not what we want for the disambiguation
case. It's not what the pure version of the code does.

Note that the updated test also passes before this patch, but it
wouldn't have passed in native-code mode once we start using the
nodetree for disambiguating nodeid prefixes.

Differential Revision: https://phab.mercurial-scm.org/D4163

# 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)