We default "short name" to a mangled version of the repository name, which is often "good enough" (looks like all repos here don't have short-name explicitly set), but we don't consider it a "short name" for this feature.

Right now, a few of my repos (The ones with the confusing names) show the /source/short-name.git, and most show /diffusion/<id>/short-name.git, which I suspect would ends up confusing for users.

We don't consider the "clone name" to be a "short name" for the purposes of this feature because it is not guaranteed to be unique (many different names mangle down to the same "clone name", and repositories are not required to have unique names in the first place).

Ahh, that makes sense.
The UI is a little confusing around this though, because it refers to both "clone name" and "repository slug" as "short name" in the manage page; I'll try to break that up a bit?

Maybe just remove "Clone As" completely? e.g., only show:

Short Name: the-short-name

...or:

Short Name: None (or just don't show anything idk)