rust: rustlazyancestors.__contains__
This changeset provides a Rust implementation of
the iteration performed by lazyancestor.__contains__
It has the advantage over the Python iteration to use
the 'seen' set encapsuled into the dedicated iterator (self._containsiter),
rather than storing emitted items in another set (self._containsseen),
and hence should reduce the memory footprint.
Also, there's no need to convert intermediate emitted revisions back into
Python integers.
At this point, it would be tempting to implement the whole lazyancestor object
in Rust, but that would lead to more C wrapping code (two objects) for
little expected benefits.
Our full contribution guidelines are in our wiki, please see:
https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).