hide more output

[Ricardo Wurmus]

Hi Guix,

when installing a few packages we see output like this:

--8<---------------cut here---------------start------------->8---
$ guix install zile-on-guile vim-full
The following packages will be installed:
   zile-on-guile 2.4.14-0.fd09781
   vim-full      8.2.0411

9.4 MB will be downloaded:
   /gnu/store/vf7w4yiax38ra7x8aqqvbnc38c0ldgpm-zile-on-guile-2.4.14-0.fd09781
   /gnu/store/dnj9wljcck9vdwgp7dwxk00qnnk1g3c5-vim-full-8.2.0411
downloading from 
https://ci.guix.gnu.org/nar/lzip/dnj9wljcck9vdwgp7dwxk00qnnk1g3c5-vim-full-8.2.0411...
 vim-full-8.2.0411  8.9MiB                 7.6MiB/s 00:01 [##################] 
100.0%

downloading from 
https://ci.guix.gnu.org/nar/lzip/vf7w4yiax38ra7x8aqqvbnc38c0ldgpm-zile-on-guile-2.4.14-0.fd09781...
 zile-on-guile-2.4.14-0.fd09781  140KiB    1.8MiB/s 00:00 [##################] 
100.0%

The following derivation will be built:
   /gnu/store/d9xms78917w67xq71pqsx5x9s6dmq6d7-profile.drv
The following graft will be made:
   /gnu/store/4n6dmg6iwjg0adpcvqygr9wgsnclswss-vim-full-8.2.0411.drv
applying 8 grafts for 
/gnu/store/4n6dmg6iwjg0adpcvqygr9wgsnclswss-vim-full-8.2.0411.drv...
building /gnu/store/d9xms78917w67xq71pqsx5x9s6dmq6d7-profile.drv...
--8<---------------cut here---------------end--------------->8---

While I’m sure many of us have gotten used to this I think we don’t need
to show quite as much information.  My proposal is to hide the
“downloading from <really long URL>” by default, because the URLs don’t
really matter to users.  We can unhide that bit of info when slightly
higher verbosity is requested.

What do you think?

--
Ricardo