Previously, if you'd run 'guix pull' after a couple of weeks, it would
fill your screen with package names, which is unhelpful.
* guix/scripts/pull.scm (ellipsis): New procedure.
(display-new/upgraded-packages): Add #:concise?.
[list->enumeration]: New procedure.
Use it instead of 'string-join'.
(display-profile-news): Pass #:concise? #t.