Fix git-rev-list "date order" with --topo-order

Fix git-rev-list "date order" with --topo-order

This fixes git-rev-list so that when there are multiple branches, we still
sort the heads in proper approximate date order even when sorting the
output topologically.

This makes things like

	gitk --all -d

work sanely and show the branches in date order (where "date order" is
obviously modified by the paren-child dependency requirements of the
topological sort).

The trivial fix is to just build the "work" list in date order rather than
inserting the new work entries at the beginning.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>