git merge between different repositories

Question

I created a repository with git-svn from a big svn repository (git svn clone). I've several local commits in my git repository that I don't need to push to svn but I will need to get updates from it.

Now I realized that I don't need the entire svn history in my local repository, since it's using too much space (some Gb) and that I should have used the -r option in the clone command to select a starting point.

I'd linke to start over with a new repository and then merge all the local commits from the old repository, but I'm not sure there is a simple way to do this.

The situation is this:

log of the old repository:

• local commit 10
• local commit 9 ...
• local commit 1
• svn revision X
• svn revision X-1 ...
• svn revision 1

the new repository has just one commit, corresponding to the contend of the revision X of the svn repository.

I tried to use format-patch and apply commands but I'm not sure on how to do this.

Is there a way to do what I need?

Thanks for any help

Answer 1

One method is, in your new repository:

• to git remote add old your old repository;
• to git fetch old;
• to checkout the branch which contains you want;
• to know the starting point from where your branch was created before the changes;
• and then use git rebase --onto.

When done, git remote rm the old repo and git gc.

See git help rebase for the --onto option: it is very, very useful.

Answer 2

You could begin with checking out the revision X from the SVN repository and getting rid of all SVN-related folders. Then git init && git add . && git commit -m "Importing revision X from SVN". Now you've got a Git repository with a snapshot of SVN's revision X.

Afterwards you could use git format-patch to create patches from your old Git repository. git format-patch x.. where x is the commit equivalent to revision X from SVN. It will generate patch files. Execute it in the old Git repository.

Subsequently, in the new repository you can git am all_those_patches.* to get them applied in the new repository.

Cf. man git-am, man git-format-patch.