errors: introduce StateError and use it from commands and cmdutil...
errors: introduce StateError and use it from commands and cmdutil
This very similar to an earlier patch (which was for `InputError`).
In this patch, I also updated the transplant extension only because
`test-transplant.t` would otherwise have needed a `#if continueflag`.
Differential Revision:
https://phab.mercurial-scm.org/D9310
