go/build: fixes for windows paths

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

src/pkg/go/build/path.go

@@ -10,7 +10,6 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
-	"strings"
 )
 
 // Path is a validated list of Trees derived from $GOROOT and $GOPATH at init.
@@ -96,7 +95,7 @@ func FindTree(path string) (tree *Tree, pkg string, err os.Error) {
 		}
 		for _, t := range Path {
 			tpath := t.SrcDir() + string(filepath.Separator)
-			if !strings.HasPrefix(path, tpath) {
+			if !filepath.HasPrefix(path, tpath) {
 				continue
 			}
 			tree = t
@@ -123,9 +122,13 @@ func FindTree(path string) (tree *Tree, pkg string, err os.Error) {
 }
 
 // isLocalPath returns whether the given path is local (/foo ./foo ../foo . ..)
+// Windows paths that starts with drive letter (c:\foo c:foo) are considered local.
 func isLocalPath(s string) bool {
 	const sep = string(filepath.Separator)
-	return strings.HasPrefix(s, sep) || strings.HasPrefix(s, "."+sep) || strings.HasPrefix(s, ".."+sep) || s == "." || s == ".."
+	return s == "." || s == ".." ||
+		filepath.HasPrefix(s, sep) ||
+		filepath.HasPrefix(s, "."+sep) || filepath.HasPrefix(s, ".."+sep) ||
+		filepath.VolumeName(s) != ""
 }
 
 var (

src/pkg/path/filepath/path.go

@@ -38,7 +38,7 @@ const (
 // Getting Dot-Dot right,''
 // http://plan9.bell-labs.com/sys/doc/lexnames.html
 func Clean(path string) string {
-	vol := volumeName(path)
+	vol := VolumeName(path)
 	path = path[len(vol):]
 	if path == "" {
 		return vol + "."

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)
+}

src/pkg/path/filepath/path_unix.go

@@ -11,8 +11,13 @@ func IsAbs(path string) bool {
 	return 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)
+}

src/pkg/path/filepath/path_windows.go

@@ -4,9 +4,11 @@
 
 package filepath
 
+import "strings"
+
 // IsAbs returns true if the path is absolute.
 func IsAbs(path string) (b bool) {
-	v := volumeName(path)
+	v := VolumeName(path)
 	if v == "" {
 		return false
 	}
@@ -17,9 +19,10 @@ func IsAbs(path string) (b bool) {
 	return path[0] == '/' || path[0] == '\\'
 }
 
-// volumeName return leading volume name.  
+// VolumeName returns leading volume name.  
-// If given "C:\foo\bar", return "C:" on windows.
+// Given "C:\foo\bar" it returns "C:" under windows.
-func volumeName(path string) (v string) {
+// On other platforms it returns "".
+func VolumeName(path string) (v string) {
 	if len(path) < 2 {
 		return ""
 	}
@@ -32,3 +35,12 @@ func volumeName(path string) (v string) {
 	}
 	return ""
 }
+
+// HasPrefix tests whether the path p begins with prefix.
+// It ignores case while comparing.
+func HasPrefix(p, prefix string) bool {
+	if strings.HasPrefix(p, prefix) {
+		return true
+	}
+	return strings.HasPrefix(strings.ToLower(p), strings.ToLower(prefix))
+}