Changes to Strasheela files are most suitably provided in the form of patches. Two approaches for creating a patch are explained here. The first approach uses Subversion (svn), the second uses diff. Subversion is more powerful (e.g., it can assure that you compare your changes to the very last version of Strasheela), whereas diff may be more simple to use. However, using Subversion is recommended.
First install the Subversion client software, for example, from here (on Linux, svn may already be installed). You then check out (i.e. download) the Strasheela repository with the following instruction (at the commandline). This will create a new directory strasheela into your current directory and copy the full Strasheela repository into it.
svn co https://strasheela.svn.sourceforge.net/svnroot/strasheela strasheela
You can now freely edit you newly created local copy. However, we discourage you from moving and deleting files (you may of course propose it on the Strasheela-devel mailing list). You can tell Subversion that you added a file (or directory) with the following command.
svn add /path/to/the/added/file
After you finished your changes, you are ready to create a patch. However, you should first update your local copy by integating all changes to the central repository since your checkout. Move into the toplevel Strasheela directory.
cd /my/path/to/strasheela
Then update your local copy.
svn update
You can now create the patch.
svn diff > myPatch.diff
Please send your patch together with an explanation to the Strasheela-devel mailing list.
NB: Subversion is a centralised revision control system. This means, that important features (e.g. commiting changes to the repository) are not available to you before you are registered as Strasheela developer at https://sourceforge.net/projects/strasheela/.
BTW: There also exist graphical user interfaces for Subversion (e.g. TortoiseSVN for Windows.
diff is usually already available on Linux and MacOS. For Windows, it can be found here (installing the setup program implicitly installs the dependencies). Enter the following command invocation at the commandline. Please replace originalStrasheelaDirectory with the path to an unchanged Strasheela directory of the latest release and editedStrasheelaDirectory with your edited version of this release.
diff -ru originalStrasheelaDirectory editedStrasheelaDirectory > myPatch.diff
Please send your patch together with an explanation to the Strasheela-devel mailing list.