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.
#require test-repo pyflakes
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:(**.py or grep("^#!.*python")) - removed()' 2>/dev/null \
> | xargs pyflakes 2>/dev/null