topic: internal config option to fix hg pick behavior (issue6406) After some consideration, hg pick was made to always use current topic (and topic namespace), even if it's not set, in which case the resulting changeset will not have any topic. Previously the intended behavior was to only update topic if there was an active topic, and not touch commit extras at all otherwise. That wasn't ideal, since pick doesn't change active topic, and amending the just-picked commit would unset its topic without clear user's intent to do so and to their surprise.