Running Phabricator 3e10f69570c0eb007f85917e16a249ea70d2dda8 from the stable branch.
When I look at a the latest commit in a Diffusion, in the Details window I see a References HEAD -> master with a link which looks like this https://dev.marples.name/source/parpd/browse/HEAD%2520-%253E%2520master/;74045ea881357edd2d29fd15ea55f236bc289446
You can currently see this in action here.
Clicking it shows what looks like a snapshot of the files at this commit, but then looks like I'm on a branch called HEAD -> master. Clicking this then gives this error
Unexpected object type from `git cat-file`: HEAD -> master missing
I notice that on this site, the Reference HEAD -> master link on the latest commit looks like this (just picking the current latest commit) https://secure.phabricator.com/rP9f3cde4db7654499c1ed565fbf048b8e8710f70a