Avoid exporting SATURNIN_SUBCOMMAND directly

Scripts may need it (eg. if using `saturnin__runhook()`) but exporting
it in the middle of main script makes it harder to see the scope
clearly and also is ugly.

Tweak the saturnin__runsc syntax so that it's not dependent on this
being global and export the SATURNIN_SUBCOMMAND only for the actual
subcommand binary call.

src/bin/satcmd.skel

         *)              break;                          ;;
     esac done
     subcommand="$1"; shift
-    export SATURNIN_SUBCOMMAND="$subcommand"
-    debug -v SHELLFU_PATH SATURNIN_LIBEXEC SHELLFU_INIGREP_PATH SATURNIN_SUBCOMMAND
+    debug -v subcommand
+    debug -v SHELLFU_PATH SATURNIN_LIBEXEC SHELLFU_INIGREP_PATH
     debug "\$*='$*'"
     case "$subcommand" in
         conf)               inigrep "$@"    ;;
         _lsfun)             shellfu-get lsfun ;;
         _lsmod)             shellfu-get lsmod ;;
         _ffrun)             ffrun "$@" ;;
-        *)                  saturnin__runsc "$@" ;;
+        *)                  saturnin__runsc "$subcommand" "$@" ;;
     esac
 }
 

src/shellfu/saturnin.sh

     #
     # Run subcommand $SATURNIN_SUBCOMMAND
     #
-    local binpath   # path to subconnand's binary
+    local subcommand="$1"; shift
+    local binpath   # path to subcommand's binary
     binpath+="$SATURNIN_LIBEXEC/"
-    binpath+="$SATURNIN_LIBEXEC_PREFIX$SATURNIN_SUBCOMMAND"
+    binpath+="$SATURNIN_LIBEXEC_PREFIX$subcommand"
     debug -v binpath
     debug "\$*='$*'"
     test -x "$binpath" || {
-        warn "invalid sub-command: $SATURNIN_SUBCOMMAND"
+        warn "invalid sub-command: $subcommand"
         saturnin__help
         return "$SHELLFU_EXIT_USAGE"
     }
-    "$binpath" "$@"
+    SATURNIN_SUBCOMMAND="$subcommand" "$binpath" "$@"
 }
 
 saturnin__usage() {