mercurial/txnutil.py

histedit: backout changeset 6f0b7475cf9a

Before 6f0b7475cf9a, histedit (like rebase) was only creating markers on final
success from the old-rewritten node to the newly created nodes (as of before
6f0b7475cf9a). In case of abort the aborted attempt were stripped to restore the
repository in its state prior to the attempt.

This use of strip was on purpose. Using markers in this case introduces various
issues. The main one is that keeping the partial result of histedit as obsolete
prevents us to recreates the same nodes in a second attempt. The same operation
will lead to an identical results, using an identical node that already exists
in the repository as obsolete.

To conclude, we cannot and should not switch to obsolescence markers creation on
histedit --abort and we backout 6f0b7475cf9a. A test to catch this class of
issue will be introduced in the next changeset.

# 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)