* guix/scripts/refresh.scm (%options): Add `--select'. (show-help): Likewise. Augment initial help text. (guix-refresh)[core-package?]: New procedure. Use it when selecting packages.
* guix/gnu-maintenance.scm (ftp-server/directory)[quirks]: Add glib. (package-update-path, download-tarball, package-update, update-package-source): New procedures. * guix/gnupg.scm, guix/scripts/refresh.scm: New files. * Makefile.am (MODULES): Add them. * guix/utils.scm (file-extension): New procedure.