"Unreleased" link broken

[rekmarks]

The Unreleased URL is at least sometimes generated in a broken state, e.g.:

[unreleased]: https://github.com/MetaMask/post-message-stream.git/v3.0.0...HEAD

The above 404s. The correct URL would be:

[unreleased]: https://github.com/MetaMask/post-message-stream/compare/v3.0.0...HEAD

It's also unclear to me whether it should force-lowercase unreleased? It overwrote a link with Unreleased in my testing.

[Gudahtt]

I can't reproduce this. It seems to always be upper-case in my testing, and I haven't seen that mangled URL used yet.

[Gudahtt]

After speaking with @rekmarks about this, our best guess is that this error was encountered with an older version of this repo. Closing for now since we can't repro this.