merge with stable

https: use web.cacerts configuration from local repo to validate remote repo

extensions: warn about invalid extensions when listing disabled commands Invalid extensions in hgext/ could in some cases cause a crash when searching for unknown commands in disabled extensions. With this change we issue a warning if extracting commands from the extensions fails. Traceback is available on request. Reported on https://bugzilla.redhat.com/show_bug.cgi?id=663183 with forest.py.