Use variable to hold shellfu() sub-command

src/shellfu.sh.skel

 __SHELLFU_IMPORTED=${__SHELLFU_IMPORTED:-}
 
 shellfu() {
+    local cmd=$1; shift
 
     # debug on import
     case $SHELLFU_DEBUGINIT:$1 in
             ;;
     esac
 
-    case $1 in
+    case $cmd in
         __debug)
             $SHELLFU_DEBUGINIT || return 0
-            shift
             echo "debug: $*" >&2
             ;;
         __die)
-            shift
             echo "$@" >&2
             test -z "$PS1" && exit 3
             return 3
             ;;
         __warn)
-            shift
             echo "$@" >&2
             ;;
 
         import)
             #
-            # Import module named $2
+            # Import module named $1
             #
-            local mname=$2
+            local mname=$1
             shellfu _is_imported "$mname" && return 0
             if shellfu _do_import "$mname";
             then
             ;;
         try_import)
             #
-            # Try if module $2 could be imported
+            # Try if module $1 could be imported
             #
-            local mname=$2
+            local mname=$1
             ( shellfu _do_import "$mname" )
             ;;
 
         _do_import)
             #
-            # Really import module named $2
+            # Really import module named $1
             #
             $SHELLFU_EMBEDDED && return 0
-            local mname=$2
+            local mname=$1
             local es=4
             local mpath
             shellfu __debug "importing module $mname"
             ;;
         _is_imported)
             #
-            # True if module $2 is already imported
+            # True if module $1 is already imported
             #
-            local mname=$2
+            local mname=$1
             echo "$__SHELLFU_IMPORTED" | tr : \\n | grep -qx "$mname"
             ;;
 
         _list_mfiles)
             #
-            # Find module files of module matching $2 (wildcard expression)
+            # Find module files of module matching $1 (wildcard expression)
             #
-            local ex="${2:-*}"
+            local ex="${1:-*}"
             local incdir
             echo "$SHELLFU_INCLUDE-sh:$SHELLFU_INCLUDE-$SHELLFU_COMPAT:$SHELLFU_PATH" \
               | tr ":" '\n' \
             ;;
         _select_mfile)
             #
-            # Select file that contains module named $2
+            # Select file that contains module named $1
             #
-            shellfu _list_mfiles "$2" | head -1
+            shellfu _list_mfiles "$1" | head -1
             ;;
 
         *)
-            shellfu __die "unknown shellfu command: $1"
+            shellfu __die "unknown shellfu command: $cmd"
             ;;
     esac
 }