annotate mercurial/txnutil.py @ 48180:f78d8b8c46d7

setup: stop packaging python3.dll and python3X.dll in the wheel distribution

Now that exewrapper is smart enough to find the DLLs it needs without help from
the build script, backout ed286d150aa8 and 2960b7fac966.  Note that this will
require deleting the build/lib.win-amd64-3.X directory to actually remove it
from the final wheel.

Differential Revision: https://phab.mercurial-scm.org/D11455

# 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)