How to merge only existing files but not delete missing files

Hi

I'm trying to find a setup which allows me to interact with a writeprotected repository.

Orig: This is a SVN repo which i cannot check out with git svn. Dunno
why, but thats not the problem. I just create a new Git branch and
check it out inside. After the merge, this repo can be deleted.

Delta: This Git repo containes only files changed from Orig.

This means that Delta containes a subset of files from Orig. The changes in Delta will have to be applied to Orig before compliling.

So i have tried various approaches and killed/recreated my Git repo a fiew times already. All i really want to do is merge the files from Delta into Orig while keeping the changes of Delta. But since Delta is a subset of Orig, all files not included in Delta will get deleted.

How i expected it to work:

1. create branch Orig and check out latest source from svn
2. merge files from Delta into orig but do not delete anything

But with this all the files not present in Delta will be deleted in Orig.

I guess i just don't understand how Git really works. But there are no tutorials for this specific situation. So what can i do?

regards,

Adrian Stern