RE: Best way to merge two repos with same content, different history

-----Original Message-----
From: Avery Pennarun [mailto:apenwarr@gmail.com]
Sent: Friday, June 05, 2009 12:01 PM
To: Kelly F. Hickel
Cc: git@vger.kernel.org
Subject: Re: Best way to merge two repos with same content, different
history

On Fri, Jun 5, 2009 at 12:30 PM, Kelly F. Hickel [off-list ref]
wrote:

quoted

       Stated another way, I have two repositories, "new" and "old",
where the files in the initial commit on branch "B1" in "new" have
exactly the same content as the last commit on branch "B1" in "old".
There also exist various branches in "new" based on "B1".  I'd like

to

quoted

merge all the commits from "new" into "old", but the SHA1s are
different, presumably because the history leading up to those points

are

quoted

different.

       Other than using manually format-patch on every branch in new,
then applying the patches (presumably with regular old patch, since

the

quoted

ancestor commit IDs won't match), is there any "good" way to merge

"new"

quoted

into "old"?

The usual replacement for "manually using format-patch" is to use "git
rebase."  It does pretty much exactly what you're describing, assuming
you don't do too many complicated merges in the meantime.

Another option is to use the .git/info/grafts file.  Here's a brief
intro: http://git.or.cz/gitwiki/GraftPoint

You'd use that to pretend the parent of your top-skimmed branch is
actually the equivalent commit in your new branch.  Then could run
"git filter-branch" to make the graft permanent, and get all your
users to switch to the new repository.

Or you could skip the filter-branch stuff and keep the really hold
history somewhere else, available for use if someone installs the
graft in their local repo.  This would lead to a smaller repository in
the general case.  (I gather that's what the Linux kernel does for
per-2.6.11 versions.)

Have fun,

Avery

Thanks Avery,
	This appears to be just what I was looking for!  I'll fiddle with it a bit to see if I can convince it to work for me.


Thanks,
	Kelly