I was trying to download and install weave on an IPv6-only host. git.io has no AAAA records, so impossible to reach. On an IPv4 enabled host, I use curl to see where the URL is redirected to

The s option keeps curl from outputting any transfer stats and the I only outputs the response headers. Pipe to grep which only returns lines matching the pattern.

$ curl -sI https://git.io/weave | grep 'Location:'
Location: https://github.com/weaveworks/weave/releases/download/latest_release/weave?

Bingo! It's pointing to https://github.com/weaveworks/weave/releases/download/latest_release/weave?, which is kind of sad, since github.com isn't IPv6 enabled either...