For releases it looks like we also upload source files to ftp. We'll need to move these to s3 as well for bug 1100624. Once the build artifacts are working, this might be as simple as extending the list of artifacts to include SOURCE_UPLOAD_FILES.

The real tricky part is going to be figuring out how to make them useful. Right now, people can browse the directories on FTP to find the source tarballs, but that won't necessarily be the case with S3. Are we going to implement directory indexes on top of s3? Or link from the website? Or something else?

The indexed artifact browser might suffice for a replacement of browsing directories: https://tools.taskcluster.net/index/artifacts/#/ We will be updating & adding new routes as well in bug 1133074 in order to make them easier to get to for certain tools, and perhaps for people as well. I don't know if that addresses your concern, though.

In the short term we'll still have post_upload on the new upload host, so nothing to do for bug 1165405.