Improve common/progress_bar.sh based on shellcheck:

- remove useless array declarations
  - remove unused variables
  - remove $ prefix for variable names in arithmetic expressions
  - normalize indentation (2 spaces)

common/progress_bar.sh

@@ -1,4 +1,4 @@
-
+# shellcheck shell=bash
 # $Id$
 
 set -e
@@ -15,11 +15,9 @@ declare -r  ERASE_LINE=${CSI}$'2K'
 declare -r  FRAME_OPEN=${CSI}$'2G['
 declare -r  FRAME_CLOSE=${CSI}$'63G]'
 declare -r  TS_POSITION=${CSI}$'65G'
-declare -r  LINE_WRAP_OFF=${CSI}$'?7l'
-declare -r  LINE_WRAP_ON=${CSI}$'?7h'
-declare -a  RESET_LINE=${CURSOR_OFF}${ERASE_LINE}${FRAME_OPEN}${FRAME_CLOSE}
+declare -r  RESET_LINE=${CURSOR_OFF}${ERASE_LINE}${FRAME_OPEN}${FRAME_CLOSE}
 
-declare -a  GRAPHIC_STR="| / - \\ + "
+declare -r  GRAPHIC_STR="| / - \\ + "
 declare -i  SEC=0  # Seconds accumulator
 declare -i  PREV_SEC=0
 
@@ -57,14 +55,14 @@ while true ; do
 
     # A BASH internal variable, the number of seconds the script
     # has been running. modulo convert to 0-59
-    SEC=$(($SECONDS % 60))
+  SEC=$((SECONDS % 60))
 
     # Detect rollover of the seconds.
   (( PREV_SEC > SEC )) && write_or_exit "${RESET_LINE}"
   PREV_SEC=$SEC
 
     # Display the accumulated time. div minutes.. modulo seconds.
-    write_or_exit "${TS_POSITION}$(($SECONDS / 60)) min. $SEC sec"
+  write_or_exit "${TS_POSITION}$((SECONDS / 60)) min. $SEC sec"
 done
 
 exit