Please consider allowing scanning tarball/zip distributions of source directly as well. It is a SCM-agnostic method that is also well-supported by GitHub, Gitiles, hgweb, and many old but still-in-use projects that pre-date Git.
It would be nice if this could be mentioned a bit clearer in the blog post and/or README; it's not really that obvious at all and I had to go to the source to check, and loads of people here seem confused about it since it more or less implies "we looked at all open source projects".