view contrib/genosxversion.py @ 39496:2f9f7889549b

snapshot: introduce an intermediate `_refinedgroups` generator

This method will be used to improve the search for a good snapshot base. To
keep things simpler, we introduce the necessary function before doing any
delta base logic change. The next handful of commits will focus on refactoring
the code to let that new logic land as clearly as possible.

# General Idea

Right now, the search for a good delta base stop whenever we found a good one.
However, when using sparse-revlog, we should probably try a bit harder.

We do significant effort to increase delta re-use by jumping on "unrelated"
delta chains that provide better results. Moving to another chain for a better
result is good, but we have no guarantee we jump at a reasonable point in that
new chain. When we consider over the chains related to the parents, we start
from the higher-level snapshots. This is a way to consider the snapshot closer
to the current revision that has the best chance to produce a small delta. We
do benefit from this walk order when jumping to a better "unrelated" stack.

To counter-balance this, we'll introduce a way to "refine" the result. After a
good delta have been found, we'll keep searching for a better delta, using the
current best one as a starting point.

# Target Setup

The `finddeltainfo` method is responsible for the general search for a good
delta. It requests candidates base from `_candidategroups` and decides which
one are usable.

The `_candidategroups` generator act as a top-level filter, it does not care
about how we pick candidates, it just does basic filtering, excluding
revisions that have been tested already or that are an obvious misfit.

The `_rawgroups` generator is the one with the actual ancestors walking logic,
It does not care about what would do a good delta and what was already tested,
it just issues the initial candidates.

We introduce a new `_refinedgroup` function to bridge the gap between
`_candidategroups` and `_rawgroups`. It delegates the initial iteration logic
and then performing relevant refining of the valid base once found. (This
logic is yet to be added to function)

All these logics are fairly independent and easier to understand when standing
alone, not mixed with each other. It also makes it easy to test and try
different approaches for one of those four layers without affecting the other
ones.

# Technical details

To communicate `finddeltainfo` choice of "current best delta base" to the
`_refinegroup` logic, we plan to use python co-routine feature. The
`_candidategroups` and `_refinegroup` generators will become co-routine. This
will allow `_refinegroup` to detect when a good delta have been found and
triggers various refining steps.

For now, `_candidategroups` will just pass the value down the stack.

After poking at various option, the co-routine appears the best to keep each
layers focus on its duty, without the need to spread implementation details
across layers.

#!/usr/bin/env python2
from __future__ import absolute_import, print_function

import argparse
import json
import os
import subprocess
import sys

# Always load hg libraries from the hg we can find on $PATH.
hglib = json.loads(subprocess.check_output(
    ['hg', 'debuginstall', '-Tjson']))[0]['hgmodules']
sys.path.insert(0, os.path.dirname(hglib))

from mercurial import util

ap = argparse.ArgumentParser()
ap.add_argument('--paranoid',
                action='store_true',
                help=("Be paranoid about how version numbers compare and "
                      "produce something that's more likely to sort "
                      "reasonably."))
ap.add_argument('--selftest', action='store_true', help='Run self-tests.')
ap.add_argument('versionfile', help='Path to a valid mercurial __version__.py')

def paranoidver(ver):
    """Given an hg version produce something that distutils can sort.

    Some Mac package management systems use distutils code in order to
    figure out upgrades, which makes life difficult. The test case is
    a reduced version of code in the Munki tool used by some large
    organizations to centrally manage OS X packages, which is what
    inspired this kludge.

    >>> paranoidver('3.4')
    '3.4.0'
    >>> paranoidver('3.4.2')
    '3.4.2'
    >>> paranoidver('3.0-rc+10')
    '2.9.9999-rc+10'
    >>> paranoidver('4.2+483-5d44d7d4076e')
    '4.2.0+483-5d44d7d4076e'
    >>> paranoidver('4.2.1+598-48d1e1214d8c')
    '4.2.1+598-48d1e1214d8c'
    >>> paranoidver('4.3-rc')
    '4.2.9999-rc'
    >>> paranoidver('4.3')
    '4.3.0'
    >>> from distutils import version
    >>> class LossyPaddedVersion(version.LooseVersion):
    ...     '''Subclass version.LooseVersion to compare things like
    ...     "10.6" and "10.6.0" as equal'''
    ...     def __init__(self, s):
    ...             self.parse(s)
    ...
    ...     def _pad(self, version_list, max_length):
    ...         'Pad a version list by adding extra 0 components to the end'
    ...         # copy the version_list so we don't modify it
    ...         cmp_list = list(version_list)
    ...         while len(cmp_list) < max_length:
    ...             cmp_list.append(0)
    ...         return cmp_list
    ...
    ...     def __cmp__(self, other):
    ...         if isinstance(other, str):
    ...             other = MunkiLooseVersion(other)
    ...         max_length = max(len(self.version), len(other.version))
    ...         self_cmp_version = self._pad(self.version, max_length)
    ...         other_cmp_version = self._pad(other.version, max_length)
    ...         return cmp(self_cmp_version, other_cmp_version)
    >>> def testver(older, newer):
    ...   o = LossyPaddedVersion(paranoidver(older))
    ...   n = LossyPaddedVersion(paranoidver(newer))
    ...   return o < n
    >>> testver('3.4', '3.5')
    True
    >>> testver('3.4.0', '3.5-rc')
    True
    >>> testver('3.4-rc', '3.5')
    True
    >>> testver('3.4-rc+10-deadbeef', '3.5')
    True
    >>> testver('3.4.2', '3.5-rc')
    True
    >>> testver('3.4.2', '3.5-rc+10-deadbeef')
    True
    >>> testver('4.2+483-5d44d7d4076e', '4.2.1+598-48d1e1214d8c')
    True
    >>> testver('4.3-rc', '4.3')
    True
    >>> testver('4.3', '4.3-rc')
    False
    """
    major, minor, micro, extra = util.versiontuple(ver, n=4)
    if micro is None:
        micro = 0
    if extra:
        if extra.startswith('rc'):
            if minor == 0:
                major -= 1
                minor = 9
            else:
                minor -= 1
            micro = 9999
            extra = '-' + extra
        else:
            extra = '+' + extra
    else:
        extra = ''
    return '%d.%d.%d%s' % (major, minor, micro, extra)

def main(argv):
    opts = ap.parse_args(argv[1:])
    if opts.selftest:
        import doctest
        doctest.testmod()
        return
    with open(opts.versionfile) as f:
        for l in f:
            if l.startswith('version = b'):
                # version number is entire line minus the quotes
                ver = l[len('version = b') + 1:-2]
                break
    if opts.paranoid:
        print(paranoidver(ver))
    else:
        print(ver)

if __name__ == '__main__':
    main(sys.argv)