root: add template variables pointing to repository directories
These paths are useful for GUI applications to detect changes. A GUI process
typically monitors .hg and .hg/store directories so that it will be notified
on lock/wlock deletion.
Alternatively, maybe we can add debugpaths command if we don't want to extend
the root command. I'm not sure which will be nicer.
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).