clean up extraneous stuff in main

main.go

@@ -1,3 +1,25 @@
+// msgp is a code generation tool for
+// creating methods to serialize and de-serialize
+// Go data structures to and from MessagePack.
+//
+// This package is targeted at the `go generate` tool.
+// To use it, include the following directive in a
+// go source file with types requiring source generation:
+//
+//     //go:generate msgp
+//
+// The go generate tool should set the proper environment variables for
+// the generator to execute without any command-line flags. However, the
+// following options are supported, if you need them:
+//
+//  -o = output file name (default is {input}_gen.go)
+//  -file = input file name (or directory; default is $GOFILE, which is set by the `go generate` command)
+//  -io = satisfy the `msgp.Decodable` and `msgp.Encodable` interfaces (default is true)
+//  -marshal = satisfy the `msgp.Marshaler` and `msgp.Unmarshaler` interfaces (default is true)
+//  -tests = generate tests and benchmarks (default is true)
+//
+// For more information, please read README.md, and the wiki at github.com/tinylib/msgp
+//
 package main
 
 import (
@@ -24,8 +46,7 @@ var (
 func main() {
 	flag.Parse()
 
-	// GOFILE and GOPACKAGE are
-	// set by `go generate`
+	// GOFILE is set by go generate
 	if *file == "" {
 		*file = os.Getenv("GOFILE")
 		if *file == "" {
@@ -56,8 +77,10 @@ func main() {
 	}
 }
 
-// Run writes all methods using the associated file/path and package.
-// (The package is only relevant for writing the new file's package declaration.)
+// Run writes all methods using the associated file or path, e.g.
+//
+//	err := msgp.Run("path/to/myfile.go", gen.Size|gen.Marshal|gen.Unmarshal|gen.Test)
+//
 func Run(gofile string, mode gen.Method) error {
 	if mode&^gen.Test == 0 {
 		return nil
@@ -77,6 +100,7 @@ func Run(gofile string, mode gen.Method) error {
 	return printer.PrintFile(newFilename(gofile, fs.Package), fs, mode)
 }
 
+// picks a new file name based on input flags and input filename(s).
 func newFilename(old string, pkg string) string {
 	if *out != "" {
 		if pre := strings.TrimPrefix(*out, old); len(pre) > 0 &&