We have a project that was forked a while back mostly via a copy/paste method. But there is still significant overlap between the repos.
Is it possible to retroactiv
As you don't want to "squash" your commits into a single file what you could do is:
Or you could take a look at how to merge two repositories like in this post. Like they did there you could add your "c&p repo" to the fork as a subtree, like it is explained in detail over here.
This are the steps taken in the guide:
git remote add -f c&prepo /path/to/c&prepo
git merge -s ours --no-commit c&prepo/master
git read-tree --prefix=vendor/c&prepo/ -u c&prepo/master
git commit
However even with those methods you aren't able to merge the whole repositories but only specific branches. What you could do is i.e. create a pull request (described in my first method) for each branch, which could take up some time depending on your branching model.
I don't think there actually is a solution where you can merge two different repositories while keeping their commit history and branches at the same time. Best of luck to you.
you should try something along the lines fo this:
git add remote ...
)git rebase
)