[PATCH] annotate: calculate line count correctly

[Jun Wu]

Excerpts from Jun Wu's message of 2016-10-01 14:20:05 +0100:
> # EXP-Topic extensions.debug

Sorry. I didn't realize the topic name. I have topics extension enabled but
didn't run the topic command. And it reuses the topic the parent has.

This is also one of the reasons I dislike the current topic design - I think
I should be able to commit on top of others' commits (in this case, @)
without thinking about topic names.