Update cmdline.sh

cmdline.sh

@@ -28,18 +28,8 @@ if test "${A5K_FUNCTIONS_INCLUDED:-false}" = 'false'; then
 
       if test -z "${MAIN_DIR-}"; then
         # shellcheck disable=SC3028,SC2128 # Intended: In POSIX sh, BASH_SOURCE is undefined / Expanding an array without an index only gives the first element
-        if MAIN_DIR="${BASH_SOURCE-}" && test -n "${MAIN_DIR}"; then
-          :
-        elif printf '%s\n' "${1}" | grep -q -m 1 -- 'cmdline.sh$' && MAIN_DIR="${1}"; then
-          :
-        else MAIN_DIR=''; fi
-echo '---'
-printf '%s\n' "${1}" || echo $?
-echo '---'
-printf '%s\n' "${1}" | grep -q -m 1 -- 'cmdline.sh$' || echo $?
-echo '---'
-dirname "${MAIN_DIR}" || echo $?
-echo '---'
+        if MAIN_DIR="${BASH_SOURCE-}" && test -n "${MAIN_DIR}"; then :; else MAIN_DIR="${1}"; fi
+        case "${MAIN_DIR}" in *'cmdline.sh') ;; *) MAIN_DIR='' ;; esac
 
         if test -n "${MAIN_DIR}" && MAIN_DIR="$(dirname "${MAIN_DIR}")" && MAIN_DIR="$(realpath "${MAIN_DIR}")"; then
           export MAIN_DIR