Re: Stitching together private svn repo and public git repo

On Wed, Jan 02, 2008 at 07:25:41PM +0000, Gregory Jefferis wrote:

So you have something like this in B:

Av1* -- Av1_b -- Av1_c -- Av1_d -- Av2_d* -- Av2_e -- Av3_e*

Where the * are manual merges of the offical Avn releases...

And you want this:

Av1   --       --       -- Av2   --      -- Av3
  \                          \                \
  Av1_b -- Av1_c -- Av1_d -- Av2_d -- Av2_e -- Av3_e  ???

This is a "rewrite history" job as parent lists are part of each commit. (See Linus' big bold-face warning about history re-writes.)

First of all I would add a remote for the 'A' repository so that those commits are available in the 'B' repository.

Something like: git remote add repoA /path/to/A git fetch repoA

You could then do this with a 'git filter-branch --parent-filter' to rewrite the parents of the merge commits. As far as I can see, you would need to call filter-branch once per merge to rewrite everything from the merge commit forwards. At this point all later commits would have different ids, so attempting to rewrite subsequent parent-ids in the same filter-branch invocation is probably futile.

It might be possible to use an intelligent script in a single --commit-filter invocation of filter-branch, but the script of the actual filter would have to be a bit (a lot!) more sophisticated, remember the ids of the new commits as it created them with 'git commit-tree' and merging in the repoA parents at the right points.

Leaving that aside and concentrating on the multiple filter-branch invocation option... for example, the first parent-filter script could be: sed -e 's/^$/-p <commit id of Av1>/'

( This is if you want your exisiting tree to branch from Av1 in the original repo. If you wanted to replace your tree root with a root at Av1, because your current root is just a copy of Av1 then you want: sed -e 's/<commit id of repoB's Av1 copy>/<commit id of Av1 in A>/' )

Then, for whatever the Av2_d commit's new id is, you could do a parent-filter of: sed -e 's/\(<new commit id of Av1_d>\)/\1 -p <commit id of Av2>/'

This causes the Av2_d commit to be rewritten, maintaining its original parent and adding another parent which comes from repoA. It then rewrites all the descendent commits of Av2_d to take account of this new commit id and all the subsequent new commit ids.

Now you can do similar for the next merge commit: sed -e 's/\(<new commit id of Av2_e>\)/\1 -p <commit id of Av3>/'

As noted, you end up with completely new commit objects with a completely new history, so you will screw everyone who is pulling/cloning from you.

Charles.