contrib/python-zstandard/setup.py

commit: improve the files field of changelog for merges

Currently, the files list of merge commits repeats all the deletions
(either actual deletions, or files that got renamed) that happened
between base and p2 of the merge. If p2 is the main branch, the list
can easily be much bigger than the change being merged.

This results in various problems worth improving:
- changelog is bigger than necessary
- `hg log directory` lists many unrelated merge commits, and `hg log
  -v -r commit` frequently fills multiple screens worth of files
- it possibly slows down adjustlinkrev, by forcing it to read more
  manifests, and that function can certainly be a bottleneck
- the server side of pulls can waste a lot of time simply opening the
  filelogs for pointless files (the constant factors for opening even
  a tiny filelog is apparently pretty bad)

So stop listing such files as described in the code.  Impacted merge
commits and their descendants get a different hash than they would
have without this. This doesn't seem problematic, except for
convert. The previous commit helped with that in the hg->hg case (but
if you do svn->hg twice from scratch, hashes can still change).

The rest of the description is numbers. I don't have much to report,
because recreating the files list of existing repositories is not
easy:
- debugupgradeformat and bundle/unbundle don't recreate the list
- export/import tends to choke quickly applying patches or on
  description that contain diffs,
- merge commits from the convert extension don't have the right files
  list for reasons orthogonal to the current commit
- replaying the merge with hg update/hg merge/hg revert --all/hg
  commit can end up failing in hg revert
- I wasn't sure that using debugsetparents + debugrebuilddirstate
  would really build the right thing

I measured commit time before and after this change, in a case with no
files filtered out, several files filtered out (no difference) and 5k
files filtered out (+1% time).

Recreating the 100 more recent merges in a private repo, the
concatenated uncompressed files lists goes from 1.12MB to
0.52MB. Excluding 3 merges that are not representative, then the size
goes from 570k to 15k.
I converted part of mozilla-central, and observed file list shrinking
quite a bit too, starting at the very first merge, 733641d9feaf, going
from 550 files to 10 files (although they have relatively few merges,
so they probably wouldn't care).

Differential Revision: https://phab.mercurial-scm.org/D6613

#!/usr/bin/env python
# Copyright (c) 2016-present, Gregory Szorc
# All rights reserved.
#
# This software may be modified and distributed under the terms
# of the BSD license. See the LICENSE file for details.

from __future__ import print_function

from distutils.version import LooseVersion
import os
import sys
from setuptools import setup

# Need change in 1.10 for ffi.from_buffer() to handle all buffer types
# (like memoryview).
# Need feature in 1.11 for ffi.gc() to declare size of objects so we avoid
# garbage collection pitfalls.
MINIMUM_CFFI_VERSION = '1.11'

try:
    import cffi

    # PyPy (and possibly other distros) have CFFI distributed as part of
    # them. The install_requires for CFFI below won't work. We need to sniff
    # out the CFFI version here and reject CFFI if it is too old.
    cffi_version = LooseVersion(cffi.__version__)
    if cffi_version < LooseVersion(MINIMUM_CFFI_VERSION):
        print('CFFI 1.11 or newer required (%s found); '
              'not building CFFI backend' % cffi_version,
              file=sys.stderr)
        cffi = None

except ImportError:
    cffi = None

import setup_zstd

SUPPORT_LEGACY = False
SYSTEM_ZSTD = False
WARNINGS_AS_ERRORS = False

if os.environ.get('ZSTD_WARNINGS_AS_ERRORS', ''):
    WARNINGS_AS_ERRORS = True

if '--legacy' in sys.argv:
    SUPPORT_LEGACY = True
    sys.argv.remove('--legacy')

if '--system-zstd' in sys.argv:
    SYSTEM_ZSTD = True
    sys.argv.remove('--system-zstd')

if '--warnings-as-errors' in sys.argv:
    WARNINGS_AS_ERRORS = True
    sys.argv.remove('--warning-as-errors')

# Code for obtaining the Extension instance is in its own module to
# facilitate reuse in other projects.
extensions = [
    setup_zstd.get_c_extension(name='zstd',
                               support_legacy=SUPPORT_LEGACY,
                               system_zstd=SYSTEM_ZSTD,
                               warnings_as_errors=WARNINGS_AS_ERRORS),
]

install_requires = []

if cffi:
    import make_cffi
    extensions.append(make_cffi.ffi.distutils_extension())
    install_requires.append('cffi>=%s' % MINIMUM_CFFI_VERSION)

version = None

with open('c-ext/python-zstandard.h', 'r') as fh:
    for line in fh:
        if not line.startswith('#define PYTHON_ZSTANDARD_VERSION'):
            continue

        version = line.split()[2][1:-1]
        break

if not version:
    raise Exception('could not resolve package version; '
                    'this should never happen')

setup(
    name='zstandard',
    version=version,
    description='Zstandard bindings for Python',
    long_description=open('README.rst', 'r').read(),
    url='https://github.com/indygreg/python-zstandard',
    author='Gregory Szorc',
    author_email='[e-mail]',
    license='BSD',
    classifiers=[
        'Development Status :: 4 - Beta',
        'Intended Audience :: Developers',
        'License :: OSI Approved :: BSD License',
        'Programming Language :: C',
        'Programming Language :: Python :: 2.7',
        'Programming Language :: Python :: 3.4',
        'Programming Language :: Python :: 3.5',
        'Programming Language :: Python :: 3.6',
        'Programming Language :: Python :: 3.7',
    ],
    keywords='zstandard zstd compression',
    packages=['zstandard'],
    ext_modules=extensions,
    test_suite='tests',
    install_requires=install_requires,
)