perf: add a `--timing` argument to `perfhelper-tracecopies` The new argument will help picking better pair for benchmarking. See documentation for details.

ui: manage logger instances and event filtering by core ui The setup code in blackbox needs more tweaks since it has lots of black magics. I'll fix them by follow-up patches. To be clear, the goal of this series is to provide a proper way for command server to install its own logger. I need it to debug in-memory repository cache.

extensions: add "uipopulate" hook, called per instance, not per process In short, this is the "reposetup" function for ui. It allows us to modify ui attributes without extending ui.__class__. Before, the only way to do that was to abuse the config dictionary, which is copied across ui instances. See the next patch for usage example.

hgweb: load globally-enabled extensions explicitly Before, extensions were loaded as a side effect of hg.repository() if the hgweb was executed as a CGI/WSGI. I want to make it explicit so that another ui hook can be inserted after extensions.loadall().

tests: disable remotefilelog on Windows I've spent a non trivial amount of time trying to eliminate the test errors, but it's looking like this is pretty dependent on Unix support. For example, there are attempts to delete open files, and uses of threads that report I/O attempts on closed files. (Maybe this is a race condition? Don't we usually use processes as workers on Windows?) In any event, I don't want real new errors elsewhere to be masked by these known problems. For some reason $CACHEDIR is reported as missing in test-remotefilelog-repack.t, but it actually exists in the hgcloneshallow call inside shallowutil.mkstickygroupdir(). By the time the process exits, it's gone. I don't see it being removed by code that calls 'rmdir' or 'remove' in the extension itself.

perf: run 'setup' function during stub run The benchmarked function might need the content of the setup to be run in order to function properly.

perf: fallback to subset if ondisk cache is missing in perfbranchmapload If there is no branchmap on disk for that filter, it means that the cache from some subset's filter is relevant for this one. We look for it instead of aborting. That way it is much simpler to run the command in an automated way. We can now add it to `test-contrib-perf.t`.