Just to share a little more info…
The MatrixUpgrades repo now depends on a “deprecation” repo that contains a set of scripts that’ll check on and adjust any assets that are in Matrix 5.4 but missing in 5.5. The way we chose to link those two together was via a git submodule which requires a hard coded URL in the upgrades repo pointing at the deprecation repo - because we maintain those repos on an internal Git repository the pointer is at our internal Git repo, meaning people who only have access to GitHub.
Because of the hard coded internal URL, even if we put the deprecations repo up on GitHub, it’d still be non-trivial to link the two back together from a clone off GitHub.
We’d like to sort it out in the long run, but in the mean time we’re happy to manually provide a packaged copy of MatrixUpgrades + deprecations to anyone who has access to the GitHub if it comes through a channel where we can share the file and verify access (as Bart says, Squiz Support is probably the most reliable).
Re tag confusion on GitHub - the 5-* tags are only showing up in some interfaces in GitHub, they’re definitely there in the underlying repository, but I’m not sure if the glitch is an oddity in the GitHub UI or the way we’re replicating the repo on to GitHub at this stage.