This script can enumerate git path diff listed in .repo/manifest.xml
$ ./comp-manifest.rb --help
Usage: [operation(default:"2 - 1")] <origin home dir(1)> <target home dir(2)> [<..>]
./comp-manifest.rb "2 - 1" ~/work/s ~/work/master
If you want to list up new gits introduced by Android S from Android R
$ ./comp-manifest.rb ~/work/s ~/work/r
Note that you need to do repo init before executing the above.
(But you may not need to do repo sync if you want to list up only).
If you want to list up new gits introduced by Android S from Android R and you'd like to filter out only in master
$ ./comp-manifest.rb "2 - 1 & 3" ~/work/s ~/work/r ~/work/master