cmd/bundle: add blank line before package declaration

so that the bundled package doesn't clobber the package declaration
of the host package.

Also: minor comment tweaks.

Change-Id: I28ab3aca2b02213edc95c6b12c0d1a2514453cfe
Reviewed-on: https://go-review.googlesource.com/18040
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

cmd/bundle/main.go

@@ -17,8 +17,8 @@
 // - no file in the package imports "C", that is, uses cgo.
 // - no file in the package has GOOS or GOARCH build tags or file names.
 // - comments associated with the package or import declarations,
-//   or associated with no top-level declaration at all,
-//   may be discarded.
+//   may be discarded, as may comments associated with no top-level
+//   declaration at all.
 // - neither the original package nor the destination package contains
 //   any identifiers starting with the designated prefix.
 //   (This allows us to avoid various conflict checks.)
@@ -31,8 +31,6 @@
 // and embedded fields of renamed types.  No methods are renamed, so we
 // needn't worry about preserving interface satisfaction.
 //
-// TODO(adonovan): gofmt the result.
-//
 package main
 
 import (
@@ -125,7 +123,7 @@ func bundle(w io.Writer, initialPkg, dest, prefix string) error {
 	fmt.Fprintf(&out, "// Code generated by golang.org/x/tools/cmd/bundle command:\n")
 	fmt.Fprintf(&out, "//   $ bundle %s %s %s\n\n", initialPkg, dest, prefix)
 
-	// Concatenate package comments from of all files.
+	// Concatenate package comments from all files...
 	for _, f := range info.Files {
 		if doc := f.Doc.Text(); strings.TrimSpace(doc) != "" {
 			for _, line := range strings.Split(doc, "\n") {
@@ -133,6 +131,8 @@ func bundle(w io.Writer, initialPkg, dest, prefix string) error {
 			}
 		}
 	}
+	// ...but don't let them become the actual package comment.
+	fmt.Fprintln(&out)
 
 	// TODO(adonovan): don't assume pkg.name == basename(pkg.path).
 	fmt.Fprintf(&out, "package %s\n\n", filepath.Base(dest))

cmd/bundle/testdata/out.golden

@@ -3,6 +3,7 @@
 
 // The package doc comment
 //
+
 package dest
 
 import (