missing explanation of Stage 4 in GCC Development Plan document

[Gerald Pfeifer]

fOn Tue, 28 Apr 2015, Richard Biener wrote:
>>> Stage 2 has been missing for 7 years now, Stages 3 and 4 seem to blur
>>> together, the "regression only" rule is more like "non-invasive fixes
>>> only" (likewise for the support branches).
>> Don't stage3 and stage4 differ in that substantial changes are still 
>> allowed for backends in stage3?
> stage3 is for _general_ bugfixing while stage4 is for _regression_ bugfixing.

I am wondering, do we want to keep this "forever", or adjust to
the fact that stage 2 has been non-existent for a while?

We may not want to redefine stage 3 to 2 and stage 4 to 3, but could 
use stage A, B, and C?  (Or in fact alpha, beta, and RC phases which
is what this essentially has become?)

Gerald