Add known rubies completion for install subcommand

scripts/completion

@@ -33,6 +33,15 @@ __rvm_gemsets ()
   echo "$(rvm gemset list | \grep -v gemset 2>/dev/null)"
 }
 
+__rvm_known ()
+{
+  # Strips comments and expands known patterns into each variation
+  rvm list known | sed 's/#.*$//' | sed '
+    s/^(\([^)]*\))\(.*\)(\([^)]*\))$/\1\2\3 \1\2 \2\3 \2/
+    s/^(\([^)]*\))\(.*\)$/\1\2 \2/
+    s/^\(.*\)(\([^)]*\))$/\1\2 \1/'
+}
+
 _rvm_commands ()
 {
   local cur=${COMP_WORDS[COMP_CWORD]}
@@ -105,13 +114,19 @@ _rvm_gemset ()
   fi
 }
 
+_rvm_install ()
+{
+  __rvm_comp "$(__rvm_known)"
+}
+
 _rvm ()
 {
   local prev=${COMP_WORDS[COMP_CWORD-1]}
 
   case "${prev}" in
   use)      _rvm_use ;;
   gemset)   _rvm_gemset ;;
+  install)  _rvm_install ;;
   *)        _rvm_commands ;;
   esac