Bug Fix: do: no safeguard to do twice

Tests item is not marked done before attempting to mark item as "done".

tests/t1500-do.sh

@@ -69,4 +69,12 @@ TODO: $HOME/todo.txt archived.
 TODO: 3 of 3 tasks shown from $HOME/todo.txt
 EOF
 
+test_todo_session 'fail multiple do attempts' <<EOF
+>>> todo.sh -a do 3
+3: x 2009-02-13 stop
+TODO: 3 marked as done.
+
+>>> todo.sh -a do 3
+3 is already marked done
+EOF
 test_done

todo.sh

@@ -705,13 +705,18 @@ case $action in
     	todo=$(sed "$item!d" "$TODO_FILE")
     	[ -z "$todo" ] && die "$item: No such todo."
 
-    	now=`date '+%Y-%m-%d'`
-    	# remove priority once item is done
-    	sed -i.bak $item"s/^(.) //" "$TODO_FILE"
-    	sed -i.bak $item"s|^|&x $now |" "$TODO_FILE"
-    	newtodo=$(sed "$item!d" "$TODO_FILE")
-    	[ $TODOTXT_VERBOSE -gt 0 ] && echo "$item: $newtodo"
-    	[ $TODOTXT_VERBOSE -gt 0 ] && echo "TODO: $item marked as done."
+      # Check if this item has already been done
+      if [ `echo $todo | grep -c "^x "` -eq 0 ] ; then
+        now=`date '+%Y-%m-%d'`
+        # remove priority once item is done
+        sed -i.bak $item"s/^(.) //" "$TODO_FILE"
+        sed -i.bak $item"s|^|&x $now |" "$TODO_FILE"
+        newtodo=$(sed "$item!d" "$TODO_FILE")
+        [ $TODOTXT_VERBOSE -gt 0 ] && echo "$item: $newtodo"
+        [ $TODOTXT_VERBOSE -gt 0 ] && echo "TODO: $item marked as done."
+      else
+        echo "$item is already marked done"
+      fi
 		done
 	
     if [ $TODOTXT_AUTO_ARCHIVE = 1 ]; then