go/build: fixes for windows paths

R=golang-dev, mattn.jp, adg
CC=golang-dev
https://golang.org/cl/4746047

1 files changed, 7 insertions, 2 deletions

diff --git a/src/pkg/path/filepath/path_plan9.go b/src/pkg/path/filepath/path_plan9.go
index 47990e0fe0..17b873f1a9 100644
--- a/src/pkg/path/filepath/path_plan9.go
+++ b/src/pkg/path/filepath/path_plan9.go
@@ -11,8 +11,13 @@ func IsAbs(path string) bool {
 	return strings.HasPrefix(path, "/") || strings.HasPrefix(path, "#")
 }
 
-// volumeName returns the leading volume name on Windows.
+// VolumeName returns the leading volume name on Windows.
 // It returns "" elsewhere
-func volumeName(path string) string {
+func VolumeName(path string) string {
 	return ""
 }
+
+// HasPrefix tests whether the path p begins with prefix.
+func HasPrefix(p, prefix string) bool {
+	return strings.HasPrefix(p, prefix)
+}