How can I push an unrelated history as a series of new commits?

Question

I have two separate remote respositories, RemoteOld and RemoteNew.

RemoteOld
Uri: http://RemoteOld
Branches: A--B--C--D--E master

RemoteNew
Uri: http://RemoteNew
Branches: A'--B' master

I want to take all of the commits from RemoteOld and add them to RemoteNew, so that RemoteNew looks like this:

RemoteNew
Branches: A'--B'--A--B--C--D--E master

Commit A in RemoteNew/master should effectively remove all the files in RemoteNew and replace them with the files in a snapshot of RemoteOld/master at Commit A. Commits B-E should be the same between RemoteOld and RemoteNew. I need to do this without using a force push.

Answer 1

You have to rebase RemoteOld/master onto RemoteNew/master. Since both branches have the same name you will need to temporarily rename a branch:

1. Clone RemoteOld:

    git clone http://RemoteOld
    cd FolderCreatedByClone
   

2. Add RemoteNew. You can remove RemoteOld while you are at it because this won't be used anymore:

   git remote add RemoteNew http://RemoteNew
   git remote rm origin
   

3. Rename RemoteOld/master to some other name, like masterOld. Fetch the master branch from new origin. Then run git branch -a to see all the branches:

   git branch -m masterOld
   git fetch RemoteNew
   git branch -a
   

Output:

 *masterOld
 remotes/RemoteNew/master       

4. Rebase masterOld onto RemoteNew/master:

    git rebase --onto master masterOld
   

5. At this point masterOld will look like what you want RemoteNew/master to look like, so just merge masterOld into RemoteNew/master.

   git checkout master
   git merge masterOld
   

6. Push RemoteNew/master. The old master branch can be deleted.

   git branch -d masterOld
   git push