hooks: introduce goToRevisionEvent(), a new client-side hook

This hook gets fired both on timeslider load (as timeslider shows a new
revision) and when the new revision is showed to a user.

doc/api/hooks_client-side.md

@@ -193,6 +193,16 @@ Called from: src/static/js/timeslider.js
 
 There doesn't appear to be any example available of this particular hook being used, but it gets fired after the timeslider is all set up.
 
+## goToRevisionEvent
+Called from: src/static/js/broadcast.js
+
+Things in context:
+
+1. rev - The newRevision
+
+This hook gets fired both on timeslider load (as timeslider shows a new revision) and when the new revision is showed to a user.
+There doesn't appear to be any example available of this particular hook being used.
+
 ## userJoinOrUpdate
 Called from: src/static/js/pad_userlist.js
 

src/static/js/broadcast.js

@@ -336,6 +336,11 @@ function loadBroadcastJS(socket, sendSocketMsg, fireWhenAllScriptsAreLoaded, Bro
     var self = this;
     var path = revisionInfo.getPath(padContents.currentRevision, newRevision);
     debugLog('newRev: ', padContents.currentRevision, path);
+
+    hooks.aCallAll('goToRevisionEvent', {
+        rev: newRevision
+    });
+
     if (path.status == 'complete')
     {
       var cs = path.changesets;