bug#38529: Make --ad-hoc the default for guix environment proposed deprecation mechanism

["Ludovic Courtès" <ludo@gnu.org>]

Hello,

Gábor Boskovits <boskovits@gmail.com> skribis:

> So in a more algorithmic manner:
> 1. if ad-hoc and inputs-of is present at the same invocation: fail
> hard. (With an error like incompatible options present)
> 2. if only ad-hoc is present, then print a deprecation warning (yes,
> we could make this suspendable with an environment variable, like you
> described)
> 3. if only inputs-of present, then do the new behaviour.
> 4. if neither ad-hoc nor inputs-of present then
>   a. if GUIX_ENVIRONMENT_DEPRECATED is 1: do the current behaviour,
>   b. if GUIX_ENVIRONMENT_DEPRECATED is undefined, or is not 1: do the
> new behaviour.

That sounds like a good plan to me.

#4 is the trickiest, and I think it’d be good to give users a bit of
time so they can start adjusting before deprecation is in effect.

Namely, we could start by introducing ‘--inputs-of’ and emitting a
warning in case #4 to suggest the use of ‘--inputs-of’.  Apart from the
warning, case #4 would still behave the same as now.

Three (?) months later, we implement what you describe above.  Hopefully
by that time many people got used to ‘--inputs-of’.

Thoughts?

Ludo’.