Interactive rebase with pre-built script?

Hi!

At $DAYJOB, we have a lot of code flowing from a central repository to repositories which hold refinitions and ports of the code from the central repository. Often enough the people working on the porting repositories find bugs in the code from the central repository, and want to submit patches upstream.

We want to get these patches upstream in the easiest possible manner, and a clever colleague of mine came up with this recipe, to be run from the downstream repository:

   git log --reverse --format="pick %h %s" master.. -- common_paths > 
changes.txt

This gives a list of the commits changing the code in the common paths (we try to make sure to make them in separate changesets, not touching the downstream code), in a format that can be used as input to git rebase --interactive.

Now, to my question. Is there an easy way to run interactive rebase on the upstream branch with this recipe? The best we have come up with so far is

   git checkout master # the upstream branch
   git rebase -i HEAD~

and then just append everything from the generated recipe. This doesn't play well if the last commit is a merge, though (making a dummy commit and just removing it from the default rebase recipe works for that case, though).

I was thinking about using git cherry-pick with a list of commits, rebase is better at helping with conflicts and such.