mercurial/txnutil.py

split: preserve phase of commit that is being split

With this change, hg split will preserve the phase of the commit that is being
split, ignoring the phases.new-commit setting. Previously, we would use whatever
phases.new-commit was set to (unless our parent was secret, then we would be
secret even if phases.new-commit=draft).

Now, splitting a draft commit with phases.new-commit=secret does not cause the
new commits to become secret, and splitting a secret commit with
phases.new-commit=draft and a draft parent does not cause the new commits to
become draft.

Test cases and commit message taken from Kyle Lippincott's D2016 (thanks!).

Differential Revision: https://phab.mercurial-scm.org/D3819

# 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)