One difference between fossil and the other version control tools I use (git and svn) is that by default it ignores files that are not in the repository. So rather than having to set up a .gitignore to have it ignore stuff, fossil does that automatically
fossil status
To see the other files, you need to look for the extra files
fossil extra
And the really nice thing about extra, is that it does not matter where you are in the project directory structure when you issue the command, it searches the entire local-root looking for the unexpected files. This also means that fossil has a way of cleaning out any unwanted temporary files:
fossil clean
Clean prompts you to confirm every delete, so it is safe to run, but it is a nice feature when the tools you are using generate a lot of temporary or intermediate files as part of their processing.