merging multiple repositories

FIXME - test this and reword it 

> > > I have three repositories, A, B and C. I wish to bring them
> > > together to only one repository (.), where they are in a
> > > directory called ./Archive, so..  ./Archive/{A,B,C}. Then I plan
> > > at a later date to move files arbitrarily from
> > > ./Archive/{A/B/C}/Something and into ./Something{A/B/C}. (A lame
> > > example, but illustrates what I want to do).
> >
> > If this transition is meant to be persistent (IOW, the A, B and C stop
> > existing as repos on their own) you can rewrite their histories to be
> > in the directories (with git filter-branch) and just merge them in
> > one. Then the histories will look like as if they have never grown
> > separately.
> >
> I don't quite understand what you are suggesting I do.
>
> I have looked over the filter-branch manpage.
>
> What would I first do? Copy all three repositories to ./Archive/{A,B,C}?
... [show rest of quote]

Fetch, actually.

    $ mkdir combined && cd combined
    $ git init
    $ git fetch ../A master:A
    $ git fetch ../B master:B
    $ git fetch ../C master:C

> Then rewrite their histories?

There is an example at the end of git-filter-branch manpage. Search
for "To move the whole tree into a subdirectory". Just use A, B and C
instead of HEAD as last argument.

Then checkout one of the new, the rewritten, branches, and merge the
two others into it:

    $ git checkout A
    $ git merge B
    $ git merge C

That's it.