localrepo: don't allow lookup of working directory revision
It seems that repo.lookup(), which is what supports the "lookup" wire
protocol command, should not allow the working copy revision
input.
This fixes both the pull test and the convert test I just added.
Differential Revision: https://phab.mercurial-scm.org/D6215
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).