While it's a bit misleading, this probably works:

https://secure.phabricator.com/diffusion/P/browse/master/;refs/heads/stable

There's currently no formal UI for this since we didn't import refs at all until recently and use cases haven't arisen since then (T6878#167814 was the last discussion, I think).

This is likely easy to implement and mostly a UI/use-case balancing issue. Do you also want them listed in the main list view? My thinking is that they're probably almost never useful (e.g., way less useful/important than tags/branches), but having some way to browse them is maybe worthwhile.

We definitely don't want them listed out, unless "listed out somewhere" was like a special paginated place to go list thousands of refs, but even then I don't see a whole lot of use there.