view mercurial/txnutil.py @ 32515:e70d6dbde713

bundle2: move function building obsmarker-part in the bundle2 module

We move it next to similar part building functions. We will need it for the
"writenewbundle" logic. This will allow us to easily include obsmarkers in
on-disk bundle, a necessary step before having `hg strip` also operate on
markers.

(Yes, the bundle2 module was already too large, but there any many
interdependencies between its components so it is non-trivial to split, this is
a quest for another adventure.)

# 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)