1 # txnutil.py - transaction related utilities

     2 #

     3 #  Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others

     4 #

     5 # This software may be used and distributed according to the terms of the

     6 # GNU General Public License version 2 or any later version.

     7 

     8 from __future__ import absolute_import

     9 

    10 import errno

    11 

    12 from . import (

    13     encoding,

    14 )

    15 

    16 def mayhavepending(root):

    17     '''return whether 'root' may have pending changes, which are

    18     visible to this process.

    19     '''

    20     return root == encoding.environ.get('HG_PENDING')

    21 

    22 def trypending(root, vfs, filename, **kwargs):

    23     '''Open  file to be read according to HG_PENDING environment variable

    24 

    25     This opens '.pending' of specified 'filename' only when HG_PENDING

    26     is equal to 'root'.

    27 

    28     This returns '(fp, is_pending_opened)' tuple.

    29     '''

    30     if mayhavepending(root):

    31         try:

    32             return (vfs('%s.pending' % filename, **kwargs), True)

    33         except IOError as inst:

    34             if inst.errno != errno.ENOENT:

    35                 raise

    36     return (vfs(filename, **kwargs), False)