Handle functions as the value of a hooks.<name> config variable
This should make it easier for extensions to add a hook when
they're loaded.
adding dir/bar
adding foo
dir/bar
foo
adding dir/bar_2
adding foo_2
dir/bar_2
foo_2
adding a
adding c
adding b
adding d
removing a
removing c
recording removal of a as rename to b (100% similar)