uncommit: pre-indent a block in if-True for the next patch

topic: provide more information when behind count cannot be computed The behind count has been confusing for various user and the associated error message is even worth. We try to clarify it to see if that helps.

topic: show the t0 even if topic is not yet touched

topics: improve the description if topic is not touched Instead of an empty stack in `hg stack` when topic does not contain any changeset, we show `not yet touched`.