Add '-l' to rds shell script for feature parity with aurora shell script

bin/aurora/shell

@@ -10,6 +10,7 @@ usage() {
   echo "  -i <infrastructure>    - infrastructure name"
   echo "  -r <aurora_name>       - RDS name (as defined in the Dalmatian config)"
   echo "  -e <environment>       - environment name (e.g. 'staging' or 'prod')"
+  echo "  -l                     - list available ec2 instance ids (optional)"
   echo "  -I <ecs_instance_id>   - ECS instance ID to connect through (optional)"
   exit 1
 }
@@ -20,7 +21,7 @@ then
  usage
 fi
 
-while getopts "i:e:r:I:h" opt; do
+while getopts "i:e:r:I:lh" opt; do
   case $opt in
     i)
       INFRASTRUCTURE_NAME=$OPTARG
@@ -34,6 +35,9 @@ while getopts "i:e:r:I:h" opt; do
     I)
       ECS_INSTANCE_ID=$OPTARG
       ;;
+    l)
+      LIST=1
+      ;;
     h)
       usage
       ;;
@@ -51,6 +55,16 @@ if [[
   usage
 fi
 
+if [ -n "$LIST" ];
+then
+  echo "==> Finding ECS instances..."
+  INSTANCES=$(aws ec2 describe-instances --filters Name=instance-state-code,Values=16 Name=tag:Name,Values="$INFRASTRUCTURE_NAME-$ENVIRONMENT*")
+
+  AVAILABLE_INSTANCES=$(echo "$INSTANCES" | jq -r '.Reservations[].Instances[] | (.InstanceId) + " | " + (.Tags[] | select(.Key == "Name") | .Value) + " | " + (.LaunchTime)')
+  echo "$AVAILABLE_INSTANCES"
+  exit 0
+fi
+
 # Remove dashes from the variables to create the RDS identifier, because dashes
 # aren't allowed in RDS identifiers. Dalmatian removes them on deployment, so we
 # need to remove them here to get the correct identifier.