Add netcat support from command line

wait-for-it.sh

@@ -15,6 +15,7 @@ Usage:
                                 Alternatively, you specify the host and port as host:port
     -s | --strict               Only execute subcommand if the test succeeds
     -q | --quiet                Don't output any status messages
+    -nc | --netcat              Force to use netcat instead of bash tcp detection
     -t TIMEOUT | --timeout=TIMEOUT
                                 Timeout in seconds, zero for no timeout
     -- COMMAND ARGS             Execute command with args after the test finishes
@@ -32,7 +33,7 @@ wait_for()
     WAITFORIT_start_ts=$(date +%s)
     while :
     do
-        if [[ $WAITFORIT_ISBUSY -eq 1 ]]; then
+        if [[ $WAITFORIT_ISBUSY -eq 1 ]] || [[ $WAITFORIT_NETCAT -eq 1 ]]; then
             nc -z $WAITFORIT_HOST $WAITFORIT_PORT
             WAITFORIT_result=$?
         else
@@ -85,6 +86,10 @@ do
         WAITFORIT_QUIET=1
         shift 1
         ;;
+        -nc | --netcat)
+        export WAITFORIT_NETCAT=1
+        shift 1
+        ;;
         -s | --strict)
         WAITFORIT_STRICT=1
         shift 1
@@ -140,6 +145,7 @@ WAITFORIT_TIMEOUT=${WAITFORIT_TIMEOUT:-15}
 WAITFORIT_STRICT=${WAITFORIT_STRICT:-0}
 WAITFORIT_CHILD=${WAITFORIT_CHILD:-0}
 WAITFORIT_QUIET=${WAITFORIT_QUIET:-0}
+export WAITFORIT_NETCAT=${WAITFORIT_NETCAT:-0}
 
 # Check to see if timeout is from busybox?
 WAITFORIT_TIMEOUT_PATH=$(type -p timeout)