Subversion is a huge program with many dependencies, and writing a small test program outside of the code body is not so easily possible.
True, you can copy a function and change it and hook into an existing command, but it litters the code and takes up valuable time that you could spend coding what you had in mind instead.
So I made a patch that plugs in a command line option and a function, and thus sets up an instant playground for you.
Seasoned devs might not find this toy very useful, but casual submitters, rookie coders and tourists who just want to poke around the code without too much effort might find this to be just the ticket that makes starting to play easy. Also, if you want to explore one of the APIs that Subversion uses (APR for example), this patch is for you.
All I need now for perfect happiness is an 'unpatch' tool that removes this patch when it's no longer needed from the resulting patch, without touching any other work that people did!