--rollback does not always roll back generation

[Marco van Hulten]

Hello—

guix package --rollback usually rolls back from generation N to N-1
(for any integer N > 0), but this didn't happen when I did this (I
wanted the last generation not to be overwritten—that part worked):

    $ guix package --switch-generation=1
    switched from generation 2 to 1
    $ mv guix-profile-2-link guix-profile-2-link~
    $ guix package -i make autoconf automake glibc-utf8-locales glibc-locales
    $ guix package --rollback
    switched from generation 2 to 2
    $ guix package --rollback
    switched from generation 2 to 2

This appears a bug to me.

guix package --switch-generation=1 worked fine, though.

—Marco