Reapply old changes when using some other SVC

You've stored changes without history.
The commit you started from in your SVC: master/HEAD.
The commit with your old changes: abc (based on same code as in master/HEAD).
The commit with latest development from your SVC: main/HEAD.

$ git checkout master
$ git checkout --patch abc
[Confirm all patches with a[ENTER].]
$ git commit
$ git merge main