rebase: pull out project-independent settings from the for loop

This makes the code a bit easier to read by doing all the project
independent settings first instead of repeating it for every for
loop iteration.

Change-Id: I4ff21296e444627beba2f4b86561069f5e9a0d73
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/233554
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>