I found a nice open library on GitHub, I imported it into my Android Studio project using Gradle dependencies, but then I realized I need to make little modifications on it.
You need to add your own git respository as remote
. You can't however do this within Android Studio, according to this thread. Use the command line instead:
git remote add remoteName remoteUrl
git fetch remoteName
Then you can go to Android Studio, VCS > Git > Pull
and select your added remote repository.