template: add successors template The successors templates display the closest visible successors of each changeset, we may have gap, like in this case: A -> B -> C -> D If we display A, C and D but not B, we can't display than B is the closest successor of A because it's not displayed. We display C as the closest successor of A instead.

test-drop.t
test-inhibit.t
test-simple4server.t
tests/test-simple4server-bundle2.t