view mercurial/txnutil.py @ 47049:25d36300ba8e stable

Backed out changeset 9b8f326731ac

Unfortunately, disabling the rust extensions means newer
Mercurial versions no longer have the persistent-nodemap
feature enabled.
This means a Mercurial 5.8.1 on RPM-based Linux distributions
will no longer be able to read repositories created
by a Mercurial 5.8 on RPM-based Linux distributions.

This violates the compatibility rules
(see https://www.mercurial-scm.org/wiki/CompatibilityRules ).

For this reason, I have to backout this change.
I'll try to find another solution to the 'hg purge' crashes.

Differential Revision: https://phab.mercurial-scm.org/D10918

# 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)