Is there a size limit for Blot's git repos?

There is no hard limit to repository size but there is a soft-cap of 1TB for bandwidth and storage combined per year per blog. That's only really a courtesy limit – at that point I would be losing quite a bit of money hosting your site and would want you to self-host Blot on your own infrastructure.

There is limit baked into the server for a single git push of a gigabyte, which practically means that files on git should be less than a gigabyte in size. Git itself would probably be unbearable to use with such large files though, but that's another question.

More generally, I've written about my thinking on bandwidth and storage restrictions.