share: stop using 'islocal' with repo instance
Having this level of polymorphism of the `islocal` function is weird, and we
already have a way to know if the repo is local from the object itself.
We are about to deprecate passing a non-bytes object to `islocal`, so clean this
up beforehand.
We might want to clean up this function too in the future, however this is
another adventure.
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).