view mercurial/txnutil.py @ 37837:e0f30c91dfd8

log: cache diffopts instance

It appears that calling patch.diff*opts() repeatedly has some cost.

  $ hg log -T '{rev}\n' -R mercurial --time > /dev/null
  (orig) time: real 4.430 secs (user 4.370+0.000 sys 0.050+0.000)
  (new)  time: real 1.950 secs (user 1.880+0.000 sys 0.060+0.000)

'diffopts or {}' isn't necessary as patch.diff*opts() accepts opts=None.

# 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)