Restic backup timeout

Does the restic command support a timeout option?
Imagine a particular repository is unavailable when restic is run. It seems the process would wait forever for the repository to become available again.

Not that I know. But there’s no general “wait forever” in restic backup. I have a repo myself that’s down right now and if I try to back up to it, I get an error right away and restic exits. So if you are having that problem, please be more specific about the symtoms, show the output, etc. Perhaps there’s something to look into further with the particular backend you’re using.