It should be fairly trivial to teach mumblr to know when it needs to rebuild the site. We could use features of content-addressing to make it happen.

Mumblr reads the markdown files from the user's WebNative filesystem at /public/Posts/. Because that directory is stored in IPFS, it has a Content ID, or CID, that represents a hash of the directory's contents. When building the site, mumblr stores the generated assets in /public/Apps/mumblr/. It would be simple for mumblr to store the CID for /public/Posts/ in a flat file alongside the generated assets.

Mumblr would simply check the current CID of /public/Posts/ against the CID stored in /public/Apps/mumblr/ and, if they are different, indicate that somehow in the UI.

Content addressing has interesting design implications.