Just give em the ol one eyed fighting Kirby
This is a vim substitution technique to capture the rest of the line as a capture group.
:'<,'>s/longhorn\(.*\)/longhorn\1-rwx
This one captures pesky optional " and places it back at the end if it found
one.
:'<,'>s/longhorn\("\?\)\(.*\)/longhorn\2-rwx\1
See-also