blackbox: log working directory version
Without this, while you could see the list of commands run,
it wasn't possible to identify what they were doing, because commads
could rely on revsets (including remote input which varies over time).
blackbox: avoid creating multiple file handles for a single log
There are multiple ui objects in Mercurial that can relate to a repository,
before this change, each one would have its own file pointer, which
results in unfortunate logging behavior.
Also, any log rotation results would be bad because only the
active blackboxui object's file pointer would be refreshed.
Note that this does not prevent two long running hg commands for the same
repository from causing problems.
tests: mock getpid to reduce glob usage
Updating tests based on
ac49ecb2a897.