deal with weave --help|help locally

thus making them unaffected by docker breakages

Fixes #1322.

weave

@@ -29,6 +29,7 @@ usage() {
     cat >&2 <<EOF
 Usage:
 
+weave --help | help
 weave setup
 weave version
 weave launch        [--password <password>] [--nickname <nickname>]
@@ -70,7 +71,7 @@ where <peer>     = <ip_address_or_fqdn>[:<port>]
       <endpoint> = [tcp://][<ip_address>]:<port> | [unix://]/path/to/socket
       <peer_id>  = <nickname> or weave internal peer ID
 EOF
-    exit 1
+    exit ${1:-1}
 }
 
 exec_remote() {
@@ -161,29 +162,42 @@ dns_arg_count() {
     fi
 }
 
+# "--help|help" are special because we always want to process them
+# locally.
+#
 # "run" is a special case because we want to use docker directly,
 # rather than the docker in $EXEC_IMAGE remotely. That's because we
 # are passing arbitrary arguments on to docker run, and we can't rely
 # on our baked-in docker to support those arguments.
-if [ "$1" = "run" ] ; then
-    shift 1
-    check_docker_version
-    if [ "$1" != "--without-dns" ] ; then
-      DNS_ARGS=$(exec_remote dns-args "$@" || true)
-    fi
-    shift $(dns_arg_count "$@")
-    collect_cidr_args "$@"
-    shift $CIDR_ARG_COUNT
-    CONTAINER=$(docker $DOCKER_CLIENT_ARGS run -e WEAVE_CIDR=none $DNS_ARGS -d "$@")
-    exec_remote attach $CIDR_ARGS --or-die $CONTAINER >/dev/null
-    echo $CONTAINER
-    exit 0
-elif [ "$1" != "--local" ] ; then
-    exec_remote "$@"
-    exit $?
-fi
+case "$1" in
+    --help|help)
+        ;;
+    run)
+        shift 1
+        check_docker_version
+        if [ "$1" != "--without-dns" ] ; then
+            DNS_ARGS=$(exec_remote dns-args "$@" || true)
+        fi
+        shift $(dns_arg_count "$@")
+        collect_cidr_args "$@"
+        shift $CIDR_ARG_COUNT
+        CONTAINER=$(docker $DOCKER_CLIENT_ARGS run -e WEAVE_CIDR=none $DNS_ARGS -d "$@")
+        exec_remote attach $CIDR_ARGS --or-die $CONTAINER >/dev/null
+        echo $CONTAINER
+        exit 0
+        ;;
+    --local)
+        shift 1
+        ;;
+    *)
+        exec_remote "$@"
+        exit $?
+        ;;
+esac
 
-shift 1
+if [ "$1" = "--help" -o "$1" = "help" ] ; then
+    usage 0
+fi
 
 BASE_IMAGE=$DOCKERHUB_USER/weave
 IMAGE=$BASE_IMAGE:$IMAGE_VERSION