As silly as it may sound, but there doesn’t seem to be a way for the HockeyApp user on Mac to sign out once he signed in…
With just a tiny bit of knowledge about how the Foundation framework offers app the ability to save preferences, I realized I can probably delete the preferences file:
$ defaults find hockey
[... huge lump of text, and somewhere in the middle:]
Found 19 keys in domain 'com.hockeyapp.mac': {
[...]
With the domain of the app figured out (maybe I could’ve just checked the app bundle’s info.plist?), it was as simple as:
$ defaults delete com.hockeyapp.mac
And now, I have been signed out!