>>> • New ‘--list-generations’ and ‘--delete-generations’ options for
>>>   ‘guix package’.

I’ve been thinking about these options, and I’m not sure how they should
work.

Will it be enough to output a generation number and a list of packages
when ‘--list-generations’ is used?  For example:

Generation 1:
guile	2.0.9	out,debug	gnu/packages/base.scm:1022:33
guile-bootstrap	2.0	out	gnu/packages/bootstrap.scm:191:3

Generation 2:
hello	2.8	out	gnu/packages/base.scm:50:2

I think we could add ‘--from’ and ‘--to’ that have to be used with the
mentioned options:

$ guix package --delete-generations 1 3 8
Deleting generations 1, 3, 8...

$ guix package --delete-generations --from=4 --to=8
Deleting generations from 4 to 8...

$ guix package --delete-generations --from=4
(Let’s assume that there are 9 generations.)
Deleting generations from 4 to 9...

$ guix package --delete-generations --to=3
(I don’t like how the above sounds.  However, I couldn’t find a better
naming scheme.)
Deleting generations from 1 to 3...

Also, I’d like to remove the dash from ‘--roll-back’ since ‘--fallback’
is written without one.

What do you think?