view mercurial/txnutil.py @ 35492:3ad582b2895c

repoview: add visibilityexceptions as an optional argument to repo.filtered()

This will help us in having an API where we can pass the filtername and the
visibilityexceptions to get a new repo object.

Visibility exceptions are the revs which must be visible even they should in
theory belong to the hidden set. They are required as there has been desire to
have a functionality to access hidden changesets using certain commands without
passing --hidden. After this patch we can make those changesets visibility
exceptions so that we can access them without requiring a unfiltered repo.

Differential Revision: https://phab.mercurial-scm.org/D1746

# 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)