view mercurial/txnutil.py @ 31195:6b098ac4542e

fileset: add a 'status(...)' predicate to control evaluation context

Same as 'revs', this predicate does not select files but switches the evaluation
context. This allow to match file according arbitrary status call. We can now
express the same query as 'hg status'.

The API (two 'revsingle' class) have been picked instead of a single 'revs'
revset for multiple reasons:

 * it is less confusing to express
 * it allow to express more query (eg: backward status, cross branch status)

# 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)