view mercurial/txnutil.py @ 46370:cad17d50736c

changelog: move branchinfo to changelogrevision

The function parses the extra dictionary after looking up the
changelogrevision. To avoid duplicated look up, it is better to provide
it as property of changelogrevision instead. Keep the function for a
release cycle as at least the topic extension depends on it.

Differential Revision: https://phab.mercurial-scm.org/D9779

# 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(b'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(b'%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)