repo: remove now-unused changectx() method (API)
repo.changectx(x) was just a synonym for repo[x], so any extensions
that fail due to this commit should switch over to that form.
Differential Revision: https://phab.mercurial-scm.org/D3037
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.