What are the persistence options for fitnesse files? So far it seems like a file system is the only thing supported. There does appear to be an out of date database plugin. Is there anything else that is supported (S3, database, etc.)? Is there a way to control where files are persisted if using the filesystem?
I believe there is very little in that area. The location of the files can be controlled using a command line option. See http://fitnesse.org/FitNesse.FullReferenceGuide.UserGuide.QuickReferenceGuide#FitNesseCommandLINE
-d /path/to/fitnesse/root
How I've used the FitNesse wiki is as a local development tool, with the pages on the file system. Once I'm satisfied with the tests I commit them to version control (e.g. git) so that they become part of the (integration) test pipeline setup (e.g. they are run as part of the CI/CD pipeline of the project).
There is a plugin I believe that will automatically commit any save actions to Git, but I've never used that. Saving each edit action just pollutes version control in my opinion. I only want to see tests after they have been checked/completed, and that tends not to be each save.
Working on a shared wiki environment (where I would expect a non-file system approach would fit in) you run into the same problem, I expect. Developing automated tests is a development task that requires some iterations before it is 'done', and not all attempts reach that 'done' state. So using shared storage for wiki persistence creates 'noise' in the test-set: which are the tests that form the current reference set that should pass and what is work in-progress.
If you are working on a larger project where new features are developed together with their automated tests it becomes even more important to know which test changes belong to which features/changes. Having tests on the file system, in version control, allows you to develop test in sync with code changes in the same branch. This is what I would recommend.