view mercurial/txnutil.py @ 38882:ff42ec7845e4

fileset: narrow status computation by left-hand-side of 'and' node

Timing with warm disk cache:

  $ hg status --cwd mozilla-central 'set:path:build/ and unknown()' --time
  (orig) time: real 1.970 secs (user 1.560+0.000 sys 0.410+0.000)
  (new)  time: real 0.330 secs (user 0.310+0.000 sys 0.020+0.000)

# 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)