evolve: refactor content-divergence resolution logic > What is the case we are looking at? This is about refactoring the part of content-div resolution logic where it decides which cset should be relocated and where. > What is a "topologicial common ancestors" vs a "greatest common ancestors"? `tca` is an ancestor which we can decide/find by looking at the at graph visually for e.g ``` c3(*) c4(*) | | c2(x) c1(x) c5 | / \ | / c0 ``` (c5 is the successor of c2 and c1) now here, `tca` of c3 and c4 is: c0 `gca` of c3 and c4 is: c5 > What is the new top-level logic/behavior that makes it better? The old code had some unnecessary edge cases just because we were using `gca`, since it can point to a revision that is not a topological ancestor. For e.g see b779b40f996e Eventually, the code around this was getting messy unnecessarily. So I looked into it and found a simple and more robust approach. And in new code, it is simple and straightforward (and easy to understand), where we handle the following 4 cases when solving content-div: 1) when both are on the same parent => (no need to do anything special, and simply proceed) 2) both are on the different parent but a) `tca` is the parent of one of them or b) there is no non-obsolete revision between `tca` and one of the divergent cset. => (relocate one to the other side and proceed) 3) both are on different parents and `tca` is not the parent of any of them and there is at least one non-obsolete cset between tca and both the divergent cset i.e (tca::div1) and (tca::div2) both the ranges have at least one non-obs revision. => (this is the case which we don't handle yet, but the solution would be to prompt the user to choose an evolve destination.) 4) both are in the parent-child relation => (both are merged and new cset will be based on the successor of `tca`) Changes in test-evolve-issue5958.t demonstrate that new code also covered case4 because in a resolution of "two divergent csets with parent-child relation" there should be one cset as a result and no orphan revs (as you can see there was an orphan before this patch).

import os
from distutils.core import setup
from os.path import dirname, join

META_PATH = 'hgext3rd/evolve/metadata.py'

def get_metadata():
    meta = {}
    fullpath = join(dirname(__file__), META_PATH)
    with open(fullpath, 'r') as fp:
        exec(fp.read(), meta)
    return meta

def get_version():
    '''Read version info from a file without importing it'''
    return get_metadata()['__version__'].decode()

def min_hg_version():
    '''Read version info from a file without importing it'''
    return get_metadata()['minimumhgversion']

py_modules = [
    'hgext3rd.serverminitopic',
]
py_packages = [
    'hgext3rd',
    'hgext3rd.evolve',
    'hgext3rd.evolve.thirdparty',
    'hgext3rd.topic',
]
py_packagedir = {
    'hgext3rd': join(dirname(__file__), 'hgext3rd')
}

py_versions = '>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, !=3.5.*, <4'

if os.environ.get('INCLUDE_INHIBIT'):
    py_modules.append('hgext3rd.evolve.hack.inhibit')
    py_modules.append('hgext3rd.evolve.hack.directaccess')

setup(
    name='hg-evolve',
    version=get_version(),
    author='Pierre-Yves David',
    author_email='pierre-yves.david@ens-lyon.org',
    maintainer='Pierre-Yves David',
    maintainer_email='pierre-yves.david@ens-lyon.org',
    url='https://www.mercurial-scm.org/doc/evolution/',
    description='Flexible evolution of Mercurial history.',
    long_description=open(join(dirname(__file__), 'README')).read(),
    keywords='hg mercurial',
    license='GPLv2+',
    py_modules=py_modules,
    packages=py_packages,
    package_dir=py_packagedir,
    python_requires=py_versions
)