view mercurial/txnutil.py @ 39845:e6d3d39cc1c7

revlog: use proper version comparison during verify

Verify appears to want to compare the changelog's revlog version
number with the version number of filelogs and error if they are
different. But what it was actually doing was comparing the full
32-bit header integer, which contains 2 shorts: 1 for the revlog
version number and 1 for feature flags.

This commit tweaks the verification code so it only looks at the
version number component of the header and emits a warning if they
differ.

The new code is more robust because it accounts for future revlog
version numbers without them needing to be special cased.

Differential Revision: https://phab.mercurial-scm.org/D4704

# 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)