hook: small refactor to store hooks as dict instead of list

We are about to take untrusted hooks into account (to report them as failures)
so we need to rearrange the code a bit to allow config overwriting each other
in a later patch.

mercurial/hook.py

@@ -162,12 +162,12 b' def _exthook(ui, repo, name, cmd, args, '
     return r
 
 def _allhooks(ui):
-    hooks = []
+    hooks = {}
     for name, cmd in ui.configitems('hooks'):
         if not name.startswith('priority'):
             priority = ui.configint('hooks', 'priority.%s' % name, 0)
-            hooks.append((-priority, len(hooks), name, cmd))
-    return [(k, v) for p, o, k, v in sorted(hooks)]
+            hooks[name] = (-priority, len(hooks), name, cmd)
+    return [(k, v) for p, o, k, v in sorted(hooks.values())]
 
 _redirect = False
 def redirect(state):