make expression shorter, now the line fits into 80 chars

serve: fix options recording, trailing whitespace

serve: allow --port=0 to specify "server chooses the port number"

rebase: improve output of hg pull --rebase (issue2072)

shrink-revlog: factor out postorder algorithm

shrink-revlog: factor out suboptimal computation

shrink-revlog: remove branchsort algorithm (it behaves poorly)

shrink-revlog: add accounting of suboptimal nodes to the new algorithms.

shrink-revlog: add "reverse postorder" and "postorder reverse" toposorts. Based on a patch by Benoit Boissinot, adapted to the pluggable sort algorithm design. toposort_reversepostorder() is a very good performer; it's designed to recreate what the revlog would have looked like if Mercurial had parent deltas now. toposort_postorderreverse() is unstable and very inconsistent, but perhaps with some work it could be made better.

shrink-revlog: add --sort option for user-selectable toposort algorithm.