The script compares 2 branches of the kernel. This specific script was written to compare branch1=ubuntu and branch2=powerkvm (IBM's), but can be easily adpated for other repositories.
The branches must exist. To run the script:
$ cd <linux-clone-dir>
$ /path/to/diff-ubuntu-pkvm.sh branch1 branch2
The result will be in the same format of a git log --pretty=oneline
command output, in the file diff_commits-final.txt.