assigning comment to ast nodes (visitee). Issue emicklei#5

cmd/protofmt/comments.proto

@@ -0,0 +1,40 @@
+/*
+ begin
+*/
+
+// comment 1
+// comment 2
+syntax = "proto"; // inline 1
+
+// comment 3
+// comment 4
+package test; // inline 2
+
+// comment 5
+// comment 6
+message Test {
+    // comment 7
+    // comment 8
+    int64 i = 1; // inline 3
+	/*
+    cstyle
+	*/
+}
+
+// comment 9
+enum Codes {
+    // comment 10
+    Unknown = 0; // inline 4
+}
+
+// comment 11
+service API {
+    // comment 12
+    rpc doit (In) returns (Out); // inline 5
+}
+
+// comment 13
+import "some.proto"; // inline 6
+
+// comment 14
+option (test.option) = 42; // inline 7

cmd/protofmt/main.go

@@ -36,7 +36,8 @@ import (
 )
 
 var (
-	overwrite = flag.Bool("w", false, "write result to (source) file instead of stdout")
+	oOverwrite = flag.Bool("w", false, "write result to (source) file instead of stdout")
+	oDebug     = flag.Bool("d", false, "dump the AST for debugging")
 )
 
 // go run *.go unformatted.proto
@@ -64,7 +65,7 @@ func readFormatWrite(filename string) error {
 	if err := format(file, buf); err != nil {
 		return err
 	}
-	if *overwrite {
+	if *oOverwrite {
 		// write back to input
 		if err := ioutil.WriteFile(filename, buf.Bytes(), os.ModePerm); err != nil {
 			return err
@@ -84,6 +85,9 @@ func format(input io.Reader, output io.Writer) error {
 	if err != nil {
 		return err
 	}
+	// if *oDebug {
+	// 	spew.Dump(def)
+	// }
 	proto.NewFormatter(output, "  ").Format(def) // 2 spaces
 	return nil
 }