[archiso] Improve help message of mkarchiso

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

archiso/mkarchiso

@@ -139,17 +139,21 @@ _usage ()
     echo " general options:"
     echo "    -p PACKAGE(S)    Package(s) to install, can be used multiple times"
     echo "    -r <command>     Run <command> inside root-image"
-    echo "    -C <file>        Config file for pacman. Default ${pacman_conf}"
+    echo "    -C <file>        Config file for pacman."
+    echo "                     Default: '${pacman_conf}'"
     echo "    -L <label>       Set a label for the disk"
+    echo "                     Default: '${iso_label}'"
     echo "    -P <publisher>   Set a publisher for the disk"
+    echo "                     Default: '${iso_publisher}'"
     echo "    -A <application> Set an application name for the disk"
+    echo "                     Default: '${iso_application}'"
     echo "    -D <install_dir> Set an install_dir. All files will by located here."
-    echo "                     Default ${install_dir}"
+    echo "                     Default: '${install_dir}'"
     echo "                     NOTE: Max 8 characters, use only [a-z0-9]"
     echo "    -w <work_dir>    Set the working directory"
-    echo "                     Default ${work_dir}"
+    echo "                     Default: '${work_dir}'"
     echo "    -o <out_dir>     Set the output directory"
-    echo "                     Default ${out_dir}"
+    echo "                     Default: '${out_dir}'"
     echo "    -v               Enable verbose output"
     echo "    -h               This message"
     echo " commands:"