view mercurial/txnutil.py @ 38573:050fbd9d103a

test-convert: demonstrate an unstable hash issue for bzr -> hg -> hg

It looks like the manifest value changing is the only difference, but I'm not
sure why it's happening.  I've got a similar divergence in a production repo
that was also converted from bzr and has an octopus merge[1].  Unlike here, the
manifest values for the destination merge commits reflect the initial merge
only, instead of all four merges agreeing like this test.

    $ hg -R src_repo manifest -r 310 --debug | grep file  # octopus fixup merge
    2d8775bc2481bd28ac87038ecdf33e1dbddc80e9 644   file1
    6adb9353a55bb8be76e71382efc724ec3ccf7ed5 644   file2

    $ hg -R src_repo manifest -r 309 --debug | grep file  # first merge
    362e7cb5163153c4989daad1a834871ae849f205 644   file1
    2c65d947191938c3ea616b7ceb7648ff3843261f 644   file2

    $ hg -R dst_repo manifest -r 273 --debug | grep file  # octopus fixup merge
    362e7cb5163153c4989daad1a834871ae849f205 644   file1
    2c65d947191938c3ea616b7ceb7648ff3843261f 644   file2

    $ hg -R dst_repo manifest -r 272 --debug | grep file  # first merge
    362e7cb5163153c4989daad1a834871ae849f205 644   file1
    2c65d947191938c3ea616b7ceb7648ff3843261f 644   file2

This divergence is espcially annoying because unlike changelog differences, I
haven't figured out a way to fix this in code.  The only way I found to work
around it is to convert up to the point of divergence, `hg bundle` the bad
revision in the source, apply it to the destination, add a line to the shamap,
and fire off the conversion again.

But I suspect that there's more to it than just the octopus merge because
I also have a commit in the same repo, done in Mercurial (well after the
conversion) that is exhibiting a similar issue (and it's not a merge commit).
I'm almost positive that it was created with 4.4 or later.  Any ideas?

[1] https://www.mercurial-scm.org/pipermail/mercurial/2018-June/050924.html

# 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)