You'd want to compare changes: see https://help.github.com/articles/comparing-commits-across-time/. You can use GITHUB's UI to merge, or you'd want to merge back changes from someone else's fork, e.g. refer to http://stackoverflow.com/questions/5606048/git-merge-from-someone-elses-fork
After that is done, you will need to run the rename script.
bash ../../doc/devtools/addonrename.sh syn tikiorg # you might get fatal errors regarding bak files, that is fine. git status # check then git clean -f