* debug-rebuild-ref-tree: Copy HEAD into RefTree
* debug-rebuild-ref-tree: Add --enable flag to turn the database on
* RefTreeDatabase: Allow ORIG_HEAD, etc. on non-bare repositories
* RefTreeDatabase: Expose bootstrap refs in getAdditionalRefs
* Fix a typo referring to RevFilter as RefFilter
* Execute ReceiveCommands via a method rather than in ReceivePack
* Modify refs in UploadPack/ReceivePack using a hook interface
* Remove PreUploadHook.onPreAdvertiseRefs
* Add an AdvertiseRefsHookChain, similar to the other hook chains
* Allow creating ReceiveCommands with a specified type
* Expose an OutputStream from ReceivePack for sending client messages
* Minor javadoc wording fixes in ReceivePack
* Extract filterCommands as a static method on ReceiveCommand