localrepo: allow wlock to be inherited This is part of a series that will allow locks to be inherited by subprocesses in limited circumstances. When allowed, the parent process will pass down requisite information to the child process by way of this environment variable.

lock.release: don't call postrelease functions for inherited locks Review feedback from Pierre-Yves David. The postrelease functions typically assume the lock is not held at all.

lock: turn prepinherit/reacquire into a single context manager Review feedback from Pierre-Yves David. This makes the overall code cleaner and less error-prone, and makes a previously explicitly checked error state impossible.