'D' marks that it is out-of-date wrt. its dependencies,
'B' marks that it is out-of-date wrt. its base).
+ TODO: Speed up by an order of magnitude
+ TODO: Graph view
+
tg update
~~~~~~~~~
Update the current topic branch wrt. changes in the branches
TODO: Some infrastructure for sharing topic branches between
repositories easily
+TODO: tg depend for adding/removing dependencies smoothly
+TODO: tg tidy for creating a one-commit-per-patch tidied up history
+ (for pulling by upstream)
IMPLEMENTATION