Add internal subcommand _ls_subcommands

src/bin/saturnin.skel

     echo ""
     echo "installed sub-commands:"
     echo ""
+    ls_subcommands | sed -e 's/^/    /'
+    return "$FFOO_EXIT_OK"
+}
+
+ls_subcommands() {
     find "$SATURNIN_LIBEXEC" \
         -mindepth 1 \
         -maxdepth 1 \
         -executable \
-      | sed -e 's/.*saturnin-/    /' \
+      | sed -e 's/.*saturnin-//' \
       | sort
-    return "$FFOO_EXIT_OK"
 }
 
 version_info() {
 shift
 
 case "$SATURNIN_SUBCOMMAND" in
-    conf)   inigrep "$@"    ;;
-    help)   print_help      ;;
-    *)      subcommand "$@" ;;
+    conf)               inigrep "$@"    ;;
+    help)               print_help      ;;
+    _ls_subcommands)    ls_subcommands ;;
+    *)                  subcommand "$@" ;;
 esac