How to merge several Git repos into one and interleave histories

Question

My situation is that I have two Git repositories that I need to merge into a single repository (there are actually more repos, but I can start with two).

The two rep

Answer 1

The solution turned out to be much more involved than I had hoped for. It involves manipulating and combining the output of two (or more) git fast-export streams, and importing them into a new repository using git fast-import.

In short, a new fast-import stream is generated by traversing two input streams, and switching back-and-forth between them based on a date-sorted log from the main branches.

I have implemented the solution in a Python script called join-git-repos.py, that I put in a GitHub repository here.