blackbox: initialize logger with repo instance The blackboxlogger is unusable without a repo. Let's simply initialize it with a repo instance.

blackbox: do not nullify repo to deactivate the logger on failure The _repo will be a mandatory attribute. Instead, make the logger to not track any events.

blackbox: extract global last logger to proxylogger class So the blackboxlogger can be instantiated with a repo.

ui: pass in bytes opts dict to logger.log() This is the convention of the Mercurial API.

ui: pass in formatted message to logger.log() This makes sure that all logger instances will handle the message arguments properly.

blackbox: send debug message to logger by core ui Since the core ui.log() may recurse into ui.log() through ui.debug(), it must guard against recursion. The ui extension class can finally be removed.

blackbox: change the way of deactivating the logger on write error This prepares for the upcoming code move. The recursion guard will be ported to the core ui.