Merge-o-Matic is Ubuntu's automated merge system (also known as "mom"). It produces automated merges of the differences between source packages in two distributions, as well as collections of useful patches to aid manual merging or review. (For instance Merge-o-Matic is used to generate merges by combining both the Ubuntu and Debian changes since their first common ancestor and leaving any conflicts to be resolved by human hand)
The target location of this tool is https://merges.ubuntu.com/
The layout of the directory generated by "mom" is the same as a Debian FTP pool, so to see the merge for debhelper see the https://merges.ubuntu.com/d/debhelper directory and to see the merge for libraw1394 see the https://merges.ubuntu.com/libr/libraw1394 directory. In each directory you will find a REPORT file that tells you what the files mean and what to do.
To grab all the relevant files for a merge, a grab-merge.sh script is available. Be sure to run it from a scratch directory as any other contents will be lost. Status pages showing the outstanding merges for each component are available, choose main, restricted, universe or multiverse.
All source code for Merge-O-Matic is available in the Bazaar version control system at Launchpad.net: https://launchpad.net/merge-o-matic