Add script to generate go protobuf code

Script can be invoked with "go generate", and also adds
or corrects the go_package compilation option in the dnstap
protobuf spec.

dnstap.go

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+//go:generate ./genproto.sh
+
 package dnstap
 
 const outputChannelSize = 32

dnstap.pb/dnstap.proto

@@ -16,7 +16,6 @@
 
 syntax = "proto2";
 package dnstap;
-
 option go_package = "github.com/dnstap/golang-dnstap;dnstap";
 
 // "Dnstap": this is the top-level dnstap type, which is a "union" type that

genproto.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+go_package() {
+	local file pkg line script
+	file=$1; shift
+	pkg=$1; shift
+
+	line="option go_package = \"$pkg\";"
+	grep "^$line\$" $file > /dev/null && return
+
+	script="/^package dnstap/|a|$line|.|w|q|"
+	if grep "^option go_package" $file > /dev/null; then
+		script="/^option go_package/d|1|${script}"
+	fi
+
+	echo "$script" | tr '|' '\n' | ed $file || exit
+}
+
+dir=$(dirname $0)
+[ -n "$dir" ] && cd $dir
+
+cd dnstap.pb
+
+go_package dnstap.proto "github.com/dnstap/golang-dnstap;dnstap"
+protoc --go_out=../../../.. dnstap.proto