Re: Joining Repositories

[Ryan Anderson <ryan@michonline.com>]

On Wed, Jan 18, 2006 at 01:51:58PM +0100, Petr Baudis wrote:
>   Hello,
> 
> Dear diary, on Wed, Jan 18, 2006 at 01:25:59PM CET, I got a letter
> where Mathias Waack <Mathias.Waack@rantzau.de> said that...
> > we're using git with cogito as a frontend. For some reasons I forgot we have 
> > some repositories which belong to the same project. To simplify the whole 
> > thing I would like to join these repositories. It mainly means to move some 
> > directories. So lets say I have: 
> > 
> > 	/r1/.git
> > 	/r2/.git
> > 
> > and what I would like to have is
> > 
> > 	/r/.git
> > 	   r1
> >            r2
> > 
> > Of course the history should remain (otherwise it would be to easy). 
> > 
> > How should I do this?
> 
>   The crucial question is what the joined repository's directory
> structure should be. If from r1/a, r2/b you want r/a, r/b then it's
> easy:
> 
> 	cd r1
> 	cg-branch-add r2 ../r2/.git
> 	cg-fetch r2
> 	cg-merge -j r2
> 
>   But if you want r1/a, r2/b to turn to r/r1/a, r/r2/b, you will have
> to rewrite the history of each (and then do the above). One rough
> and untested sketch...

... Why would that be the optimal method?

Assuming both repositories are clean, no extraneous files, and without
testing, of course:

In r1:
	mkdir r1
	# move everything into the subdirectory called r1.
	git mv $(ls -a | grep -v -e ^.git$ -e ^r1$) r1/
	git commit -a "Restructure directory"

In r2:
	mkdir r2
	# move all files into r2/
	git mv $(ls -a | grep -v -e ^.git$ -e ^r2$) r2/
	git commit -a "Restructure directory"

	git fetch ../r1/
	GIT_INDEX_FILE=.git/tmp-index git-read-tree FETCH_HEAD
	GIT_INDEX_FILE=.git/tmp-index git-checkout-cache -a -u
	git-update-cache --add -- $(GIT_INDEX_FILE=.git/tmp-index git-ls-files)
	cp .git/FETCH_HEAD .git/MERGE_HEAD
	git commit

No history rewritten, merging with the old repositories should, at least
theoretically, work, etc.

(This is just a restatement of Linus's "Coolest merge ever" / union
merge)

-- 

Ryan Anderson
  sometimes Pug Majere