dagop: split module hosting DAG-related algorithms from revset This module hosts the following functions. They are somewhat similar (e.g. scanning revisions using heap queue or stack) and seem non-trivial in algorithmic point of view. - _revancestors() - _revdescendants() - reachableroots() - _toposort() I was thinking of adding revset._fileancestors() generator for better follow() implementation, but it would be called from context.py as well. So I decided to create new module. Naming is hard. I couldn't come up with any better module name, so it's called "dag operation" now. I rejected the following candidates: - ancestor.py - existing, revlog-level DAG algorithm - ancestorset.py - doesn't always return a set - dagalgorithm.py - hard to type - dagutil.py - existing - revancestor.py - I want to add fileancestors() % wc -l mercurial/dagop.py mercurial/revset.py 339 mercurial/dagop.py 2020 mercurial/revset.py 2359 total

tests: protect tests involving git ext::sh with git-ext-sh

hghave: add has_git_range for testing if git understands ext::sh Even on CentOS 7, git is at version 1.8. It seems git 1.9 is when ext::sh was introduced so we a check for that. The way these functions are written follows the same style and format for the way we check svn and bzr versions.