commit hook support (OAK-100)

[Michael Dürig]

Hi,
In revision 1341834 I added initial support for commit hooks. That is, 
the methods of CommitHook are now called when transient changes are 
applied.

However I currently don't do a rebase before merging the changes back to 
trunk. Is there a reason we should do that? If so, shouldn't it better 
go into an upper layer (i.e. Root/Tree)? A rebase operation already 
exists there and is used by Session.refresh(true).

Probably something like this could be done:

===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/core/RootImpl.java 
(revision 1341791)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/core/RootImpl.java 
(revision )
@@ -158,6 +158,7 @@

     @Override
     public void commit() throws CommitFailedException {
+        rebase();
         purgePendingChanges();
         branch.merge();
         branch = store.branch();

Michael