Please support a way to request "stable minus N" for some N

[joshtriplett]

Problem you are trying to solve

Projects often specify their MSRV policy as "the last N stable versions" (e.g. the last 2, or the last 4).

To test that in CI, I'd love to have a syntax to install "stable minus 1" (the version before the current stable version), or similar.

Solution you'd like

I don't have a preference about the syntax; anything unambiguous would be fine. Something like stable-1 or stable-2 would be unambiguous given what's currently supported, but some other syntax could work too.

Notes

No response

[rami3l]

Indeed, I also want to have this in my workflow sometimes...
@rbtcollins what do you think about the syntax?

[rami3l]

cc #2291
(I meant to say "closing as a duplicate" but I don't have the permission...)