view hg @ 39055:ef3d3a2f9aa5

changegroup: refactor delta parent code

We had recently abstracted the delta parent functions to
facilitate extracting code from cgpacker. Now that we're in
a better place, it is time to revisit the design.

Changegroup version 1 requires that the previous node be used as the
delta parent. Later versions allow any available node to be used
as the base.

In the case where an arbitrary parent can be used, the choice of
a delta parent is best left in the hands of the storage backend.
So it makes sense for the delta parent selection to be hidden
away in the storage layer. This means deferring the choice of the
delta parent selection function to as close to delta generation
time as possible.

This commit moves the delta selection logic to essentially just
before delta generation. However, because changegroup version 1
limits what we can do, we have retained the ability to force a
delta against the previous revision.

As part of this, I realized that the ellipsis parent function was
unused! That's because ellipsis mode always sends full revisions
and not deltas.

Differential Revision: https://phab.mercurial-scm.org/D4214

#!/usr/bin/env python
#
# mercurial - scalable distributed SCM
#
# Copyright 2005-2007 Matt Mackall <[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

if os.environ.get('HGUNICODEPEDANTRY', False):
    try:
        reload(sys)
        sys.setdefaultencoding("undefined")
    except NameError:
        pass

libdir = '@LIBDIR@'

if libdir != '@' 'LIBDIR' '@':
    if not os.path.isabs(libdir):
        libdir = os.path.join(os.path.dirname(os.path.realpath(__file__)),
                              libdir)
        libdir = os.path.abspath(libdir)
    sys.path.insert(0, libdir)

# enable importing on demand to reduce startup time
try:
    if sys.version_info[0] < 3 or sys.version_info >= (3, 6):
        import hgdemandimport; hgdemandimport.enable()
except ImportError:
    sys.stderr.write("abort: couldn't find mercurial libraries in [%s]\n" %
                     ' '.join(sys.path))
    sys.stderr.write("(check your install and PYTHONPATH)\n")
    sys.exit(-1)

from mercurial import dispatch
dispatch.run()