eol: make the hook check all new heads, not only tip (
issue2666)
Report and test by Antoine Pitrou <solipsis@pitrou.net>
eol: the hook no longer requires the extension to be loaded
Reading rules in the hook means we no longer need ui to be filled and do not
need reposetup() to be run anymore.
eol: separate .hgeol parsing from merge in ui
This will help refactoring the hook.