rolling back only a single package

[cdelia]

Hi,

I upgraded guix a couple of days ago, installed some things and now I 
found that xmobar just keeps segfaulting.

Switching to specific generation it's really cool, but in this case 
would "uninstall" all the software that it's between the 
update-generation and the current one.

So, there is any way to just downgrade a single package (resolving it 
dependencies) with out doing a full switch?

I guess this it's connected to 
https://lists.gnu.org/archive/html/help-guix/2016-08/msg00028.html

And I could also switch and then manually re install. But maybe there is 
a standard or automatic way to do it.

Thanks!