Contributions to Magit are highly welcome. Here are a few guidelines that will help your patches hit upstream as soon as possible.
Please make sure your commits are well-organized and "atomic" (hitting a single well-defined target each).
Please also make sure you check that byte-compilation completes without errors or warnings, and that tests run without failures.
$ make lisp test
Bonus points if you add tests to cover the feature you're hacking.
Please submit your changes by opening a pull request on Magit's Github repository at https://github.com/magit/magit/pulls.