templatekw: deprecate old-style template keyword function (API)
.. api::
`f(**kwargs)` style template keyword function is deprecated. Switch to
new `(context, mapping)` API by declaring resource requirements.
The new-style API will be the default in Mercurial 4.9. See
registrar.templatekeyword for details.
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).