Matthew Weier O'Phinney has a recent post about recent work that's been done to split up the componenents in Zend Framework 2 into their own repositories and linked as dependencies.

Today we accomplished one of the major goals towards Zend Framework 3: splitting the various components into their own repositories. This proved to be a huge challenge, due to the amount of history in our repository (the git repository has history going back to 2009, around the time ZF 1.8 was released!), and the goals we had for what component repositories should look like. This is the story of how we made it happen.

Matthew talks about the methods that were used to split things apart, even more so than they already were. While the components could be installed separately before, the methods used to get there were "cringeworthy". He talks about the different methods they've tried and the version bump issue that came with them, even when no changes were present. He talks about the ultimate goal of the refactor and the techniques to get there - a combination of grafts, subtree, subdirectory-filter and tree-filter through git. He covers some of the "stumbling blocks" they hit along the way including empty merge commits. The end result was a one-line command that could be executed and split out the provided component (well, with a lot of help behind the scenes).

He ends the post talking about the speed of the extraction process (hint: parallel processing is a happy thing), the ultimate results of the entire framework being split and a few lessons they learned along the way.