Merging (joining/stiching/rewriting) history of "unrelated" git repositories

Hello,

I'm migrating two repositories from svn. I already did svn->git migration (git-svn clone) and now have two git repositories.

I would like to merge them into 1 git repository, but to merge also history - branches and tags.

The reason is that the svn repositories in fact represent one "project" - you had to download both of then, they are not useful separately. Tags were applied to both repositories, also list of branches is almost identical for both.

So right now I have:

    - projectA:
       master: r1, r4, r5, r7
       branch1: r10, r11, r13
    - projectB:
       master: r2, r3, r6
       branch1: r12, r14

The content of projectA and projectB is different (let's say projectA is in subfolder A and projectB is in subfolder B). So revisions on projectA branches have only A folder, and revisions on projectB branches have only B folder.

But I would like to have:

    - projectAB:
       master: r1', r2', r3', r4', r5', r6', r7'
       branch1: r10', r11', r12', r13', r14'

Where all revisions have content from both projects. For example, the r5' should have the "A" folder content the same as r5, but also should have "B" folder content the same as in r3 (because r3 was the last commit to projectB (date-wise) before commit r5 to projectA).

There's additional difficulty of handling merges...

Any suggestions on what's the best way to do it?

Currently I'm testing join-git-repos.py script (https://github.com/mbitsnbites/git-tools/blob/master/join-git-repos.py) but it's slow, memory inefficient and handles "master" branch only...

Thanks,