topic: merge _showlasttouched logic into _listtopics Makes --age work with --verbose.

topic: simplify _showlasttouched and _getlasttouched (and its data structure)

branching: merge with stable

split: add a --interactive flag While the interactive mode is useful for end-users, there are some cases where they don't need the interactivity overhead. Moreover, this allow the split command to be used in automated scripts.