* guix/scripts/publish.scm (show-help, %options): Support '-C METHOD' and '-C METHOD:LEVEL'. (default-compression): New procedure. (bake-narinfo+nar): Add lzip. (nar-response-port): Likewise. (string->compression-type): New procedure. (make-request-handler): Generalize /nar/gzip handler to handle /nar/lzip as well. * tests/publish.scm ("/nar/lzip/*"): New test. ("/*.narinfo with lzip compression"): New test. * doc/guix.texi (Invoking guix publish): Document it. (Requirements): Mention lzlib.