Inspired by Advantages of monorepos and Unorthodocs: Abandon your DVCS and Return to Sanity (what a gem!), I switched to using monorepo for the opentorah.org projects (with the number and sizes of projects, I think I am safe from the issues that Google and FaceBook experienced ;)).

One never knows when there will arise a need to split or merge repositories, so this is how I did it:

To extract directories from a repository into a separate one:

  $ git filter-repo --path <path1> --path <path2> ...

Since filter-repo does not try to preserve history for the files that were renamed, before extracting the directories, one should figure out what other directories files in them previously resided in. Looking through the output of $ git log is one way; another is to look at the renames report that $ git filter-repo --analyze generates.

To merge repository old into repository new preserving history (one hopes!):

  $ cd <new>
  $ git remote add -f old <old>
  $ git merge ald/master --allow-unrelated-histories

Since it is impossible to have a file in Git where only the last revision is kept but revision history is automatically discarded, and for the generated files (like HTML, PDF and EPUB of the papers) to be visible on the site they need to be checked in, I might end up pruning their history periodically using $ git filter-repo...