Comment by analog31

A middle ground is "just write a plug-in." What I mean is, I like programs that provide a mechanism for scripting, adding a plug-in, whatever. This allows you to add a feature and perhaps even maintain it in your own repo, without trying to manage the entire project yourself.

Of course it only works for some kinds of changes, and not total structural or cultural revision, but still it seems to be a part of many of the most vibrant open source projects.