mercurial/policy.py

copies: make _checkcopies handle copy sequences spanning the TCA (issue4028)

When working in a rotated DAG (for a graftlike merge), there can be files
that are renamed both between the base and the topological CA, and between
the TCA and the endpoint farther from the base. Such renames span the TCA
(and thus need both passes of _checkcopies to be fully detected), but may
not necessarily be divergent.

Make _checkcopies return "incomplete copies" and "incomplete divergences"
in this case, and let mergecopies recombine them once data from both passes
of _checkcopies is available.

With this patch, all known cases involving renames and grafts pass.

(Developed together with Pierre-Yves David)

# policy.py - module policy logic for Mercurial.
#
# Copyright 2015 Gregory Szorc <[e-mail]>
#
# 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 os
import sys

# Rules for how modules can be loaded. Values are:
#
#    c - require C extensions
#    allow - allow pure Python implementation when C loading fails
#    cffi - required cffi versions (implemented within pure module)
#    cffi-allow - allow pure Python implementation if cffi version is missing
#    py - only load pure Python modules
#
# By default, require the C extensions for performance reasons.
policy = 'c'
policynoc = ('cffi', 'cffi-allow', 'py')
policynocffi = ('c', 'py')

try:
    from . import __modulepolicy__
    policy = __modulepolicy__.modulepolicy
except ImportError:
    pass

# PyPy doesn't load C extensions.
#
# The canonical way to do this is to test platform.python_implementation().
# But we don't import platform and don't bloat for it here.
if '__pypy__' in sys.builtin_module_names:
    policy = 'cffi'

# Our C extensions aren't yet compatible with Python 3. So use pure Python
# on Python 3 for now.
if sys.version_info[0] >= 3:
    policy = 'py'

# Environment variable can always force settings.
policy = os.environ.get('HGMODULEPOLICY', policy)