I spent the better part of a year in a team that was merging and bug fixing our companies engine releases into the customer (and owning company) code base. We a

I spent the better part of a year in a team that was merging and bug fixing our companies engine releases into the customer (and owning company) code base. We also had to deal with different code repositories and version control systems. We ended up with a script that created a new git repository, checked out the base version of the code there. Then created a branch for our updated release and another for their codebase. Then attempted to do a merge between the two. For any files which couldn't be automatically merged it created a set of 4 files, the original then a triplet for doing a 3-way merge. This is also when I bought myself a copy of Beyond Compare 4, which fits perfectly for the price and feature set for what we needed.