build: move package sources from src/pkg to src

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

18 files changed, 3306 insertions, 0 deletions

diff --git a/src/path/example_test.go b/src/path/example_test.go
new file mode 100644
index 000000000..fa8c28d2e
--- /dev/null
+++ b/src/path/example_test.go
@@ -0,0 +1,63 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package path_test
+
+import (
+	"fmt"
+	"path"
+)
+
+func ExampleBase() {
+	fmt.Println(path.Base("/a/b"))
+	// Output: b
+}
+
+func ExampleClean() {
+	paths := []string{
+		"a/c",
+		"a//c",
+		"a/c/.",
+		"a/c/b/..",
+		"/../a/c",
+		"/../a/b/../././/c",
+	}
+
+	for _, p := range paths {
+		fmt.Printf("Clean(%q) = %q\n", p, path.Clean(p))
+	}
+
+	// Output:
+	// Clean("a/c") = "a/c"
+	// Clean("a//c") = "a/c"
+	// Clean("a/c/.") = "a/c"
+	// Clean("a/c/b/..") = "a/c"
+	// Clean("/../a/c") = "/a/c"
+	// Clean("/../a/b/../././/c") = "/a/c"
+}
+
+func ExampleDir() {
+	fmt.Println(path.Dir("/a/b/c"))
+	// Output: /a/b
+}
+
+func ExampleExt() {
+	fmt.Println(path.Ext("/a/b/c/bar.css"))
+	// Output: .css
+}
+
+func ExampleIsAbs() {
+	fmt.Println(path.IsAbs("/dev/null"))
+	// Output: true
+}
+
+func ExampleJoin() {
+	fmt.Println(path.Join("a", "b", "c"))
+	// Output: a/b/c
+}
+
+func ExampleSplit() {
+	fmt.Println(path.Split("static/myfile.css"))
+	// Output: static/ myfile.css
+}
diff --git a/src/path/filepath/example_unix_test.go b/src/path/filepath/example_unix_test.go
new file mode 100644
index 000000000..f3fe076c3
--- /dev/null
+++ b/src/path/filepath/example_unix_test.go
@@ -0,0 +1,39 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !windows,!plan9
+
+package filepath_test
+
+import (
+	"fmt"
+	"path/filepath"
+)
+
+func ExampleSplitList() {
+	fmt.Println("On Unix:", filepath.SplitList("/a/b/c:/usr/bin"))
+	// Output:
+	// On Unix: [/a/b/c /usr/bin]
+}
+
+func ExampleRel() {
+	paths := []string{
+		"/a/b/c",
+		"/b/c",
+		"./b/c",
+	}
+	base := "/a"
+
+	fmt.Println("On Unix:")
+	for _, p := range paths {
+		rel, err := filepath.Rel(base, p)
+		fmt.Printf("%q: %q %v\n", p, rel, err)
+	}
+
+	// Output:
+	// On Unix:
+	// "/a/b/c": "b/c" <nil>
+	// "/b/c": "../b/c" <nil>
+	// "./b/c": "" Rel: can't make b/c relative to /a
+}
diff --git a/src/path/filepath/export_test.go b/src/path/filepath/export_test.go
new file mode 100644
index 000000000..0cf9e3bca
--- /dev/null
+++ b/src/path/filepath/export_test.go
@@ -0,0 +1,7 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath
+
+var LstatP = &lstat
diff --git a/src/path/filepath/match.go b/src/path/filepath/match.go
new file mode 100644
index 000000000..a9bcc103c
--- /dev/null
+++ b/src/path/filepath/match.go
@@ -0,0 +1,309 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath
+
+import (
+	"errors"
+	"os"
+	"runtime"
+	"sort"
+	"strings"
+	"unicode/utf8"
+)
+
+// ErrBadPattern indicates a globbing pattern was malformed.
+var ErrBadPattern = errors.New("syntax error in pattern")
+
+// Match returns true if name matches the shell file name pattern.
+// The pattern syntax is:
+//
+//	pattern:
+//		{ term }
+//	term:
+//		'*'         matches any sequence of non-Separator characters
+//		'?'         matches any single non-Separator character
+//		'[' [ '^' ] { character-range } ']'
+//		            character class (must be non-empty)
+//		c           matches character c (c != '*', '?', '\\', '[')
+//		'\\' c      matches character c
+//
+//	character-range:
+//		c           matches character c (c != '\\', '-', ']')
+//		'\\' c      matches character c
+//		lo '-' hi   matches character c for lo <= c <= hi
+//
+// Match requires pattern to match all of name, not just a substring.
+// The only possible returned error is ErrBadPattern, when pattern
+// is malformed.
+//
+// On Windows, escaping is disabled. Instead, '\\' is treated as
+// path separator.
+//
+func Match(pattern, name string) (matched bool, err error) {
+Pattern:
+	for len(pattern) > 0 {
+		var star bool
+		var chunk string
+		star, chunk, pattern = scanChunk(pattern)
+		if star && chunk == "" {
+			// Trailing * matches rest of string unless it has a /.
+			return strings.Index(name, string(Separator)) < 0, nil
+		}
+		// Look for match at current position.
+		t, ok, err := matchChunk(chunk, name)
+		// if we're the last chunk, make sure we've exhausted the name
+		// otherwise we'll give a false result even if we could still match
+		// using the star
+		if ok && (len(t) == 0 || len(pattern) > 0) {
+			name = t
+			continue
+		}
+		if err != nil {
+			return false, err
+		}
+		if star {
+			// Look for match skipping i+1 bytes.
+			// Cannot skip /.
+			for i := 0; i < len(name) && name[i] != Separator; i++ {
+				t, ok, err := matchChunk(chunk, name[i+1:])
+				if ok {
+					// if we're the last chunk, make sure we exhausted the name
+					if len(pattern) == 0 && len(t) > 0 {
+						continue
+					}
+					name = t
+					continue Pattern
+				}
+				if err != nil {
+					return false, err
+				}
+			}
+		}
+		return false, nil
+	}
+	return len(name) == 0, nil
+}
+
+// scanChunk gets the next segment of pattern, which is a non-star string
+// possibly preceded by a star.
+func scanChunk(pattern string) (star bool, chunk, rest string) {
+	for len(pattern) > 0 && pattern[0] == '*' {
+		pattern = pattern[1:]
+		star = true
+	}
+	inrange := false
+	var i int
+Scan:
+	for i = 0; i < len(pattern); i++ {
+		switch pattern[i] {
+		case '\\':
+			if runtime.GOOS != "windows" {
+				// error check handled in matchChunk: bad pattern.
+				if i+1 < len(pattern) {
+					i++
+				}
+			}
+		case '[':
+			inrange = true
+		case ']':
+			inrange = false
+		case '*':
+			if !inrange {
+				break Scan
+			}
+		}
+	}
+	return star, pattern[0:i], pattern[i:]
+}
+
+// matchChunk checks whether chunk matches the beginning of s.
+// If so, it returns the remainder of s (after the match).
+// Chunk is all single-character operators: literals, char classes, and ?.
+func matchChunk(chunk, s string) (rest string, ok bool, err error) {
+	for len(chunk) > 0 {
+		if len(s) == 0 {
+			return
+		}
+		switch chunk[0] {
+		case '[':
+			// character class
+			r, n := utf8.DecodeRuneInString(s)
+			s = s[n:]
+			chunk = chunk[1:]
+			// We can't end right after '[', we're expecting at least
+			// a closing bracket and possibly a caret.
+			if len(chunk) == 0 {
+				err = ErrBadPattern
+				return
+			}
+			// possibly negated
+			negated := chunk[0] == '^'
+			if negated {
+				chunk = chunk[1:]
+			}
+			// parse all ranges
+			match := false
+			nrange := 0
+			for {
+				if len(chunk) > 0 && chunk[0] == ']' && nrange > 0 {
+					chunk = chunk[1:]
+					break
+				}
+				var lo, hi rune
+				if lo, chunk, err = getEsc(chunk); err != nil {
+					return
+				}
+				hi = lo
+				if chunk[0] == '-' {
+					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
+						return
+					}
+				}
+				if lo <= r && r <= hi {
+					match = true
+				}
+				nrange++
+			}
+			if match == negated {
+				return
+			}
+
+		case '?':
+			if s[0] == Separator {
+				return
+			}
+			_, n := utf8.DecodeRuneInString(s)
+			s = s[n:]
+			chunk = chunk[1:]
+
+		case '\\':
+			if runtime.GOOS != "windows" {
+				chunk = chunk[1:]
+				if len(chunk) == 0 {
+					err = ErrBadPattern
+					return
+				}
+			}
+			fallthrough
+
+		default:
+			if chunk[0] != s[0] {
+				return
+			}
+			s = s[1:]
+			chunk = chunk[1:]
+		}
+	}
+	return s, true, nil
+}
+
+// getEsc gets a possibly-escaped character from chunk, for a character class.
+func getEsc(chunk string) (r rune, nchunk string, err error) {
+	if len(chunk) == 0 || chunk[0] == '-' || chunk[0] == ']' {
+		err = ErrBadPattern
+		return
+	}
+	if chunk[0] == '\\' && runtime.GOOS != "windows" {
+		chunk = chunk[1:]
+		if len(chunk) == 0 {
+			err = ErrBadPattern
+			return
+		}
+	}
+	r, n := utf8.DecodeRuneInString(chunk)
+	if r == utf8.RuneError && n == 1 {
+		err = ErrBadPattern
+	}
+	nchunk = chunk[n:]
+	if len(nchunk) == 0 {
+		err = ErrBadPattern
+	}
+	return
+}
+
+// Glob returns the names of all files matching pattern or nil
+// if there is no matching file. The syntax of patterns is the same
+// as in Match. The pattern may describe hierarchical names such as
+// /usr/*/bin/ed (assuming the Separator is '/').
+//
+func Glob(pattern string) (matches []string, err error) {
+	if !hasMeta(pattern) {
+		if _, err = os.Lstat(pattern); err != nil {
+			return nil, nil
+		}
+		return []string{pattern}, nil
+	}
+
+	dir, file := Split(pattern)
+	switch dir {
+	case "":
+		dir = "."
+	case string(Separator):
+		// nothing
+	default:
+		dir = dir[0 : len(dir)-1] // chop off trailing separator
+	}
+
+	if !hasMeta(dir) {
+		return glob(dir, file, nil)
+	}
+
+	var m []string
+	m, err = Glob(dir)
+	if err != nil {
+		return
+	}
+	for _, d := range m {
+		matches, err = glob(d, file, matches)
+		if err != nil {
+			return
+		}
+	}
+	return
+}
+
+// glob searches for files matching pattern in the directory dir
+// and appends them to matches. If the directory cannot be
+// opened, it returns the existing matches. New matches are
+// added in lexicographical order.
+func glob(dir, pattern string, matches []string) (m []string, e error) {
+	m = matches
+	fi, err := os.Stat(dir)
+	if err != nil {
+		return
+	}
+	if !fi.IsDir() {
+		return
+	}
+	d, err := os.Open(dir)
+	if err != nil {
+		return
+	}
+	defer d.Close()
+
+	names, err := d.Readdirnames(-1)
+	if err != nil {
+		return
+	}
+	sort.Strings(names)
+
+	for _, n := range names {
+		matched, err := Match(pattern, n)
+		if err != nil {
+			return m, err
+		}
+		if matched {
+			m = append(m, Join(dir, n))
+		}
+	}
+	return
+}
+
+// hasMeta returns true if path contains any of the magic characters
+// recognized by Match.
+func hasMeta(path string) bool {
+	// TODO(niemeyer): Should other magic characters be added here?
+	return strings.IndexAny(path, "*?[") >= 0
+}
diff --git a/src/path/filepath/match_test.go b/src/path/filepath/match_test.go
new file mode 100644
index 000000000..20ec5aa2a
--- /dev/null
+++ b/src/path/filepath/match_test.go
@@ -0,0 +1,211 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath_test
+
+import (
+	"io/ioutil"
+	"os"
+	. "path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+type MatchTest struct {
+	pattern, s string
+	match      bool
+	err        error
+}
+
+var matchTests = []MatchTest{
+	{"abc", "abc", true, nil},
+	{"*", "abc", true, nil},
+	{"*c", "abc", true, nil},
+	{"a*", "a", true, nil},
+	{"a*", "abc", true, nil},
+	{"a*", "ab/c", false, nil},
+	{"a*/b", "abc/b", true, nil},
+	{"a*/b", "a/c/b", false, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxe/f", true, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxexxx/f", true, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxe/xxx/f", false, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxexxx/fff", false, nil},
+	{"a*b?c*x", "abxbbxdbxebxczzx", true, nil},
+	{"a*b?c*x", "abxbbxdbxebxczzy", false, nil},
+	{"ab[c]", "abc", true, nil},
+	{"ab[b-d]", "abc", true, nil},
+	{"ab[e-g]", "abc", false, nil},
+	{"ab[^c]", "abc", false, nil},
+	{"ab[^b-d]", "abc", false, nil},
+	{"ab[^e-g]", "abc", true, nil},
+	{"a\\*b", "a*b", true, nil},
+	{"a\\*b", "ab", false, nil},
+	{"a?b", "a☺b", true, nil},
+	{"a[^a]b", "a☺b", true, nil},
+	{"a???b", "a☺b", false, nil},
+	{"a[^a][^a][^a]b", "a☺b", false, nil},
+	{"[a-ζ]*", "α", true, nil},
+	{"*[a-ζ]", "A", false, nil},
+	{"a?b", "a/b", false, nil},
+	{"a*b", "a/b", false, nil},
+	{"[\\]a]", "]", true, nil},
+	{"[\\-]", "-", true, nil},
+	{"[x\\-]", "x", true, nil},
+	{"[x\\-]", "-", true, nil},
+	{"[x\\-]", "z", false, nil},
+	{"[\\-x]", "x", true, nil},
+	{"[\\-x]", "-", true, nil},
+	{"[\\-x]", "a", false, nil},
+	{"[]a]", "]", false, ErrBadPattern},
+	{"[-]", "-", false, ErrBadPattern},
+	{"[x-]", "x", false, ErrBadPattern},
+	{"[x-]", "-", false, ErrBadPattern},
+	{"[x-]", "z", false, ErrBadPattern},
+	{"[-x]", "x", false, ErrBadPattern},
+	{"[-x]", "-", false, ErrBadPattern},
+	{"[-x]", "a", false, ErrBadPattern},
+	{"\\", "a", false, ErrBadPattern},
+	{"[a-b-c]", "a", false, ErrBadPattern},
+	{"[", "a", false, ErrBadPattern},
+	{"[^", "a", false, ErrBadPattern},
+	{"[^bc", "a", false, ErrBadPattern},
+	{"a[", "a", false, nil},
+	{"a[", "ab", false, ErrBadPattern},
+	{"*x", "xxx", true, nil},
+}
+
+func errp(e error) string {
+	if e == nil {
+		return "<nil>"
+	}
+	return e.Error()
+}
+
+func TestMatch(t *testing.T) {
+	for _, tt := range matchTests {
+		pattern := tt.pattern
+		s := tt.s
+		if runtime.GOOS == "windows" {
+			if strings.Index(pattern, "\\") >= 0 {
+				// no escape allowed on windows.
+				continue
+			}
+			pattern = Clean(pattern)
+			s = Clean(s)
+		}
+		ok, err := Match(pattern, s)
+		if ok != tt.match || err != tt.err {
+			t.Errorf("Match(%#q, %#q) = %v, %q want %v, %q", pattern, s, ok, errp(err), tt.match, errp(tt.err))
+		}
+	}
+}
+
+// contains returns true if vector contains the string s.
+func contains(vector []string, s string) bool {
+	for _, elem := range vector {
+		if elem == s {
+			return true
+		}
+	}
+	return false
+}
+
+var globTests = []struct {
+	pattern, result string
+}{
+	{"match.go", "match.go"},
+	{"mat?h.go", "match.go"},
+	{"*", "match.go"},
+	{"../*/match.go", "../filepath/match.go"},
+}
+
+func TestGlob(t *testing.T) {
+	for _, tt := range globTests {
+		pattern := tt.pattern
+		result := tt.result
+		if runtime.GOOS == "windows" {
+			pattern = Clean(pattern)
+			result = Clean(result)
+		}
+		matches, err := Glob(pattern)
+		if err != nil {
+			t.Errorf("Glob error for %q: %s", pattern, err)
+			continue
+		}
+		if !contains(matches, result) {
+			t.Errorf("Glob(%#q) = %#v want %v", pattern, matches, result)
+		}
+	}
+	for _, pattern := range []string{"no_match", "../*/no_match"} {
+		matches, err := Glob(pattern)
+		if err != nil {
+			t.Errorf("Glob error for %q: %s", pattern, err)
+			continue
+		}
+		if len(matches) != 0 {
+			t.Errorf("Glob(%#q) = %#v want []", pattern, matches)
+		}
+	}
+}
+
+func TestGlobError(t *testing.T) {
+	_, err := Glob("[7]")
+	if err != nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+}
+
+var globSymlinkTests = []struct {
+	path, dest string
+	brokenLink bool
+}{
+	{"test1", "link1", false},
+	{"test2", "link2", true},
+}
+
+func TestGlobSymlink(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9":
+		t.Skipf("skipping on %s", runtime.GOOS)
+	case "windows":
+		if !supportsSymlinks {
+			t.Skipf("skipping on %s", runtime.GOOS)
+		}
+
+	}
+
+	tmpDir, err := ioutil.TempDir("", "globsymlink")
+	if err != nil {
+		t.Fatal("creating temp dir:", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	for _, tt := range globSymlinkTests {
+		path := Join(tmpDir, tt.path)
+		dest := Join(tmpDir, tt.dest)
+		f, err := os.Create(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := f.Close(); err != nil {
+			t.Fatal(err)
+		}
+		err = os.Symlink(path, dest)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if tt.brokenLink {
+			// Break the symlink.
+			os.Remove(path)
+		}
+		matches, err := Glob(dest)
+		if err != nil {
+			t.Errorf("GlobSymlink error for %q: %s", dest, err)
+		}
+		if !contains(matches, dest) {
+			t.Errorf("Glob(%#q) = %#v want %v", dest, matches, dest)
+		}
+	}
+}
diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go
new file mode 100644
index 000000000..d37fc9dfc
--- /dev/null
+++ b/src/path/filepath/path.go
@@ -0,0 +1,464 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package filepath implements utility routines for manipulating filename paths
+// in a way compatible with the target operating system-defined file paths.
+package filepath
+
+import (
+	"errors"
+	"os"
+	"sort"
+	"strings"
+)
+
+// A lazybuf is a lazily constructed path buffer.
+// It supports append, reading previously appended bytes,
+// and retrieving the final string. It does not allocate a buffer
+// to hold the output until that output diverges from s.
+type lazybuf struct {
+	path       string
+	buf        []byte
+	w          int
+	volAndPath string
+	volLen     int
+}
+
+func (b *lazybuf) index(i int) byte {
+	if b.buf != nil {
+		return b.buf[i]
+	}
+	return b.path[i]
+}
+
+func (b *lazybuf) append(c byte) {
+	if b.buf == nil {
+		if b.w < len(b.path) && b.path[b.w] == c {
+			b.w++
+			return
+		}
+		b.buf = make([]byte, len(b.path))
+		copy(b.buf, b.path[:b.w])
+	}
+	b.buf[b.w] = c
+	b.w++
+}
+
+func (b *lazybuf) string() string {
+	if b.buf == nil {
+		return b.volAndPath[:b.volLen+b.w]
+	}
+	return b.volAndPath[:b.volLen] + string(b.buf[:b.w])
+}
+
+const (
+	Separator     = os.PathSeparator
+	ListSeparator = os.PathListSeparator
+)
+
+// Clean returns the shortest path name equivalent to path
+// by purely lexical processing.  It applies the following rules
+// iteratively until no further processing can be done:
+//
+//	1. Replace multiple Separator elements with a single one.
+//	2. Eliminate each . path name element (the current directory).
+//	3. Eliminate each inner .. path name element (the parent directory)
+//	   along with the non-.. element that precedes it.
+//	4. Eliminate .. elements that begin a rooted path:
+//	   that is, replace "/.." by "/" at the beginning of a path,
+//	   assuming Separator is '/'.
+//
+// The returned path ends in a slash only if it represents a root directory,
+// such as "/" on Unix or `C:\` on Windows.
+//
+// If the result of this process is an empty string, Clean
+// returns the string ".".
+//
+// See also Rob Pike, ``Lexical File Names in Plan 9 or
+// Getting Dot-Dot Right,''
+// http://plan9.bell-labs.com/sys/doc/lexnames.html
+func Clean(path string) string {
+	originalPath := path
+	volLen := volumeNameLen(path)
+	path = path[volLen:]
+	if path == "" {
+		if volLen > 1 && originalPath[1] != ':' {
+			// should be UNC
+			return FromSlash(originalPath)
+		}
+		return originalPath + "."
+	}
+	rooted := os.IsPathSeparator(path[0])
+
+	// Invariants:
+	//	reading from path; r is index of next byte to process.
+	//	writing to buf; w is index of next byte to write.
+	//	dotdot is index in buf where .. must stop, either because
+	//		it is the leading slash or it is a leading ../../.. prefix.
+	n := len(path)
+	out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen}
+	r, dotdot := 0, 0
+	if rooted {
+		out.append(Separator)
+		r, dotdot = 1, 1
+	}
+
+	for r < n {
+		switch {
+		case os.IsPathSeparator(path[r]):
+			// empty path element
+			r++
+		case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
+			// . element
+			r++
+		case path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
+			// .. element: remove to last separator
+			r += 2
+			switch {
+			case out.w > dotdot:
+				// can backtrack
+				out.w--
+				for out.w > dotdot && !os.IsPathSeparator(out.index(out.w)) {
+					out.w--
+				}
+			case !rooted:
+				// cannot backtrack, but not rooted, so append .. element.
+				if out.w > 0 {
+					out.append(Separator)
+				}
+				out.append('.')
+				out.append('.')
+				dotdot = out.w
+			}
+		default:
+			// real path element.
+			// add slash if needed
+			if rooted && out.w != 1 || !rooted && out.w != 0 {
+				out.append(Separator)
+			}
+			// copy element
+			for ; r < n && !os.IsPathSeparator(path[r]); r++ {
+				out.append(path[r])
+			}
+		}
+	}
+
+	// Turn empty string into "."
+	if out.w == 0 {
+		out.append('.')
+	}
+
+	return FromSlash(out.string())
+}
+
+// ToSlash returns the result of replacing each separator character
+// in path with a slash ('/') character. Multiple separators are
+// replaced by multiple slashes.
+func ToSlash(path string) string {
+	if Separator == '/' {
+		return path
+	}
+	return strings.Replace(path, string(Separator), "/", -1)
+}
+
+// FromSlash returns the result of replacing each slash ('/') character
+// in path with a separator character. Multiple slashes are replaced
+// by multiple separators.
+func FromSlash(path string) string {
+	if Separator == '/' {
+		return path
+	}
+	return strings.Replace(path, "/", string(Separator), -1)
+}
+
+// SplitList splits a list of paths joined by the OS-specific ListSeparator,
+// usually found in PATH or GOPATH environment variables.
+// Unlike strings.Split, SplitList returns an empty slice when passed an empty string.
+func SplitList(path string) []string {
+	return splitList(path)
+}
+
+// Split splits path immediately following the final Separator,
+// separating it into a directory and file name component.
+// If there is no Separator in path, Split returns an empty dir
+// and file set to path.
+// The returned values have the property that path = dir+file.
+func Split(path string) (dir, file string) {
+	vol := VolumeName(path)
+	i := len(path) - 1
+	for i >= len(vol) && !os.IsPathSeparator(path[i]) {
+		i--
+	}
+	return path[:i+1], path[i+1:]
+}
+
+// Join joins any number of path elements into a single path, adding
+// a Separator if necessary. The result is Cleaned, in particular
+// all empty strings are ignored.
+func Join(elem ...string) string {
+	for i, e := range elem {
+		if e != "" {
+			return Clean(strings.Join(elem[i:], string(Separator)))
+		}
+	}
+	return ""
+}
+
+// Ext returns the file name extension used by path.
+// The extension is the suffix beginning at the final dot
+// in the final element of path; it is empty if there is
+// no dot.
+func Ext(path string) string {
+	for i := len(path) - 1; i >= 0 && !os.IsPathSeparator(path[i]); i-- {
+		if path[i] == '.' {
+			return path[i:]
+		}
+	}
+	return ""
+}
+
+// EvalSymlinks returns the path name after the evaluation of any symbolic
+// links.
+// If path is relative the result will be relative to the current directory,
+// unless one of the components is an absolute symbolic link.
+func EvalSymlinks(path string) (string, error) {
+	return evalSymlinks(path)
+}
+
+// Abs returns an absolute representation of path.
+// If the path is not absolute it will be joined with the current
+// working directory to turn it into an absolute path.  The absolute
+// path name for a given file is not guaranteed to be unique.
+func Abs(path string) (string, error) {
+	return abs(path)
+}
+
+func unixAbs(path string) (string, error) {
+	if IsAbs(path) {
+		return Clean(path), nil
+	}
+	wd, err := os.Getwd()
+	if err != nil {
+		return "", err
+	}
+	return Join(wd, path), nil
+}
+
+// Rel returns a relative path that is lexically equivalent to targpath when
+// joined to basepath with an intervening separator. That is,
+// Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
+// On success, the returned path will always be relative to basepath,
+// even if basepath and targpath share no elements.
+// An error is returned if targpath can't be made relative to basepath or if
+// knowing the current working directory would be necessary to compute it.
+func Rel(basepath, targpath string) (string, error) {
+	baseVol := VolumeName(basepath)
+	targVol := VolumeName(targpath)
+	base := Clean(basepath)
+	targ := Clean(targpath)
+	if targ == base {
+		return ".", nil
+	}
+	base = base[len(baseVol):]
+	targ = targ[len(targVol):]
+	if base == "." {
+		base = ""
+	}
+	// Can't use IsAbs - `\a` and `a` are both relative in Windows.
+	baseSlashed := len(base) > 0 && base[0] == Separator
+	targSlashed := len(targ) > 0 && targ[0] == Separator
+	if baseSlashed != targSlashed || baseVol != targVol {
+		return "", errors.New("Rel: can't make " + targ + " relative to " + base)
+	}
+	// Position base[b0:bi] and targ[t0:ti] at the first differing elements.
+	bl := len(base)
+	tl := len(targ)
+	var b0, bi, t0, ti int
+	for {
+		for bi < bl && base[bi] != Separator {
+			bi++
+		}
+		for ti < tl && targ[ti] != Separator {
+			ti++
+		}
+		if targ[t0:ti] != base[b0:bi] {
+			break
+		}
+		if bi < bl {
+			bi++
+		}
+		if ti < tl {
+			ti++
+		}
+		b0 = bi
+		t0 = ti
+	}
+	if base[b0:bi] == ".." {
+		return "", errors.New("Rel: can't make " + targ + " relative to " + base)
+	}
+	if b0 != bl {
+		// Base elements left. Must go up before going down.
+		seps := strings.Count(base[b0:bl], string(Separator))
+		size := 2 + seps*3
+		if tl != t0 {
+			size += 1 + tl - t0
+		}
+		buf := make([]byte, size)
+		n := copy(buf, "..")
+		for i := 0; i < seps; i++ {
+			buf[n] = Separator
+			copy(buf[n+1:], "..")
+			n += 3
+		}
+		if t0 != tl {
+			buf[n] = Separator
+			copy(buf[n+1:], targ[t0:])
+		}
+		return string(buf), nil
+	}
+	return targ[t0:], nil
+}
+
+// SkipDir is used as a return value from WalkFuncs to indicate that
+// the directory named in the call is to be skipped. It is not returned
+// as an error by any function.
+var SkipDir = errors.New("skip this directory")
+
+// WalkFunc is the type of the function called for each file or directory
+// visited by Walk. The path argument contains the argument to Walk as a
+// prefix; that is, if Walk is called with "dir", which is a directory
+// containing the file "a", the walk function will be called with argument
+// "dir/a". The info argument is the os.FileInfo for the named path.
+//
+// If there was a problem walking to the file or directory named by path, the
+// incoming error will describe the problem and the function can decide how
+// to handle that error (and Walk will not descend into that directory). If
+// an error is returned, processing stops. The sole exception is that if path
+// is a directory and the function returns the special value SkipDir, the
+// contents of the directory are skipped and processing continues as usual on
+// the next file.
+type WalkFunc func(path string, info os.FileInfo, err error) error
+
+var lstat = os.Lstat // for testing
+
+// walk recursively descends path, calling w.
+func walk(path string, info os.FileInfo, walkFn WalkFunc) error {
+	err := walkFn(path, info, nil)
+	if err != nil {
+		if info.IsDir() && err == SkipDir {
+			return nil
+		}
+		return err
+	}
+
+	if !info.IsDir() {
+		return nil
+	}
+
+	names, err := readDirNames(path)
+	if err != nil {
+		return walkFn(path, info, err)
+	}
+
+	for _, name := range names {
+		filename := Join(path, name)
+		fileInfo, err := lstat(filename)
+		if err != nil {
+			if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir {
+				return err
+			}
+		} else {
+			err = walk(filename, fileInfo, walkFn)
+			if err != nil {
+				if !fileInfo.IsDir() || err != SkipDir {
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// Walk walks the file tree rooted at root, calling walkFn for each file or
+// directory in the tree, including root. All errors that arise visiting files
+// and directories are filtered by walkFn. The files are walked in lexical
+// order, which makes the output deterministic but means that for very
+// large directories Walk can be inefficient.
+// Walk does not follow symbolic links.
+func Walk(root string, walkFn WalkFunc) error {
+	info, err := os.Lstat(root)
+	if err != nil {
+		return walkFn(root, nil, err)
+	}
+	return walk(root, info, walkFn)
+}
+
+// readDirNames reads the directory named by dirname and returns
+// a sorted list of directory entries.
+func readDirNames(dirname string) ([]string, error) {
+	f, err := os.Open(dirname)
+	if err != nil {
+		return nil, err
+	}
+	names, err := f.Readdirnames(-1)
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+	sort.Strings(names)
+	return names, nil
+}
+
+// Base returns the last element of path.
+// Trailing path separators are removed before extracting the last element.
+// If the path is empty, Base returns ".".
+// If the path consists entirely of separators, Base returns a single separator.
+func Base(path string) string {
+	if path == "" {
+		return "."
+	}
+	// Strip trailing slashes.
+	for len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) {
+		path = path[0 : len(path)-1]
+	}
+	// Throw away volume name
+	path = path[len(VolumeName(path)):]
+	// Find the last element
+	i := len(path) - 1
+	for i >= 0 && !os.IsPathSeparator(path[i]) {
+		i--
+	}
+	if i >= 0 {
+		path = path[i+1:]
+	}
+	// If empty now, it had only slashes.
+	if path == "" {
+		return string(Separator)
+	}
+	return path
+}
+
+// Dir returns all but the last element of path, typically the path's directory.
+// After dropping the final element, the path is Cleaned and trailing
+// slashes are removed.
+// If the path is empty, Dir returns ".".
+// If the path consists entirely of separators, Dir returns a single separator.
+// The returned path does not end in a separator unless it is the root directory.
+func Dir(path string) string {
+	vol := VolumeName(path)
+	i := len(path) - 1
+	for i >= len(vol) && !os.IsPathSeparator(path[i]) {
+		i--
+	}
+	dir := Clean(path[len(vol) : i+1])
+	return vol + dir
+}
+
+// VolumeName returns leading volume name.
+// Given "C:\foo\bar" it returns "C:" under windows.
+// Given "\\host\share\foo" it returns "\\host\share".
+// On other platforms it returns "".
+func VolumeName(path string) (v string) {
+	return path[:volumeNameLen(path)]
+}
diff --git a/src/path/filepath/path_plan9.go b/src/path/filepath/path_plan9.go
new file mode 100644
index 000000000..ee8912d58
--- /dev/null
+++ b/src/path/filepath/path_plan9.go
@@ -0,0 +1,34 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath
+
+import "strings"
+
+// IsAbs returns true if the path is absolute.
+func IsAbs(path string) bool {
+	return strings.HasPrefix(path, "/") || strings.HasPrefix(path, "#")
+}
+
+// volumeNameLen returns length of the leading volume name on Windows.
+// It returns 0 elsewhere.
+func volumeNameLen(path string) int {
+	return 0
+}
+
+// HasPrefix exists for historical compatibility and should not be used.
+func HasPrefix(p, prefix string) bool {
+	return strings.HasPrefix(p, prefix)
+}
+
+func splitList(path string) []string {
+	if path == "" {
+		return []string{}
+	}
+	return strings.Split(path, string(ListSeparator))
+}
+
+func abs(path string) (string, error) {
+	return unixAbs(path)
+}
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
new file mode 100644
index 000000000..399284b97
--- /dev/null
+++ b/src/path/filepath/path_test.go
@@ -0,0 +1,1028 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath_test
+
+import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+var supportsSymlinks = true
+
+type PathTest struct {
+	path, result string
+}
+
+var cleantests = []PathTest{
+	// Already clean
+	{"abc", "abc"},
+	{"abc/def", "abc/def"},
+	{"a/b/c", "a/b/c"},
+	{".", "."},
+	{"..", ".."},
+	{"../..", "../.."},
+	{"../../abc", "../../abc"},
+	{"/abc", "/abc"},
+	{"/", "/"},
+
+	// Empty is current dir
+	{"", "."},
+
+	// Remove trailing slash
+	{"abc/", "abc"},
+	{"abc/def/", "abc/def"},
+	{"a/b/c/", "a/b/c"},
+	{"./", "."},
+	{"../", ".."},
+	{"../../", "../.."},
+	{"/abc/", "/abc"},
+
+	// Remove doubled slash
+	{"abc//def//ghi", "abc/def/ghi"},
+	{"//abc", "/abc"},
+	{"///abc", "/abc"},
+	{"//abc//", "/abc"},
+	{"abc//", "abc"},
+
+	// Remove . elements
+	{"abc/./def", "abc/def"},
+	{"/./abc/def", "/abc/def"},
+	{"abc/.", "abc"},
+
+	// Remove .. elements
+	{"abc/def/ghi/../jkl", "abc/def/jkl"},
+	{"abc/def/../ghi/../jkl", "abc/jkl"},
+	{"abc/def/..", "abc"},
+	{"abc/def/../..", "."},
+	{"/abc/def/../..", "/"},
+	{"abc/def/../../..", ".."},
+	{"/abc/def/../../..", "/"},
+	{"abc/def/../../../ghi/jkl/../../../mno", "../../mno"},
+	{"/../abc", "/abc"},
+
+	// Combinations
+	{"abc/./../def", "def"},
+	{"abc//./../def", "def"},
+	{"abc/../../././../def", "../../def"},
+}
+
+var wincleantests = []PathTest{
+	{`c:`, `c:.`},
+	{`c:\`, `c:\`},
+	{`c:\abc`, `c:\abc`},
+	{`c:abc\..\..\.\.\..\def`, `c:..\..\def`},
+	{`c:\abc\def\..\..`, `c:\`},
+	{`c:\..\abc`, `c:\abc`},
+	{`c:..\abc`, `c:..\abc`},
+	{`\`, `\`},
+	{`/`, `\`},
+	{`\\i\..\c$`, `\c$`},
+	{`\\i\..\i\c$`, `\i\c$`},
+	{`\\i\..\I\c$`, `\I\c$`},
+	{`\\host\share\foo\..\bar`, `\\host\share\bar`},
+	{`//host/share/foo/../baz`, `\\host\share\baz`},
+	{`\\a\b\..\c`, `\\a\b\c`},
+	{`\\a\b`, `\\a\b`},
+}
+
+func TestClean(t *testing.T) {
+	tests := cleantests
+	if runtime.GOOS == "windows" {
+		for i := range tests {
+			tests[i].result = filepath.FromSlash(tests[i].result)
+		}
+		tests = append(tests, wincleantests...)
+	}
+	for _, test := range tests {
+		if s := filepath.Clean(test.path); s != test.result {
+			t.Errorf("Clean(%q) = %q, want %q", test.path, s, test.result)
+		}
+		if s := filepath.Clean(test.result); s != test.result {
+			t.Errorf("Clean(%q) = %q, want %q", test.result, s, test.result)
+		}
+	}
+
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Log("skipping AllocsPerRun checks; GOMAXPROCS>1")
+		return
+	}
+
+	for _, test := range tests {
+		allocs := testing.AllocsPerRun(100, func() { filepath.Clean(test.result) })
+		if allocs > 0 {
+			t.Errorf("Clean(%q): %v allocs, want zero", test.result, allocs)
+		}
+	}
+}
+
+const sep = filepath.Separator
+
+var slashtests = []PathTest{
+	{"", ""},
+	{"/", string(sep)},
+	{"/a/b", string([]byte{sep, 'a', sep, 'b'})},
+	{"a//b", string([]byte{'a', sep, sep, 'b'})},
+}
+
+func TestFromAndToSlash(t *testing.T) {
+	for _, test := range slashtests {
+		if s := filepath.FromSlash(test.path); s != test.result {
+			t.Errorf("FromSlash(%q) = %q, want %q", test.path, s, test.result)
+		}
+		if s := filepath.ToSlash(test.result); s != test.path {
+			t.Errorf("ToSlash(%q) = %q, want %q", test.result, s, test.path)
+		}
+	}
+}
+
+type SplitListTest struct {
+	list   string
+	result []string
+}
+
+const lsep = filepath.ListSeparator
+
+var splitlisttests = []SplitListTest{
+	{"", []string{}},
+	{string([]byte{'a', lsep, 'b'}), []string{"a", "b"}},
+	{string([]byte{lsep, 'a', lsep, 'b'}), []string{"", "a", "b"}},
+}
+
+var winsplitlisttests = []SplitListTest{
+	// quoted
+	{`"a"`, []string{`a`}},
+
+	// semicolon
+	{`";"`, []string{`;`}},
+	{`"a;b"`, []string{`a;b`}},
+	{`";";`, []string{`;`, ``}},
+	{`;";"`, []string{``, `;`}},
+
+	// partially quoted
+	{`a";"b`, []string{`a;b`}},
+	{`a; ""b`, []string{`a`, ` b`}},
+	{`"a;b`, []string{`a;b`}},
+	{`""a;b`, []string{`a`, `b`}},
+	{`"""a;b`, []string{`a;b`}},
+	{`""""a;b`, []string{`a`, `b`}},
+	{`a";b`, []string{`a;b`}},
+	{`a;b";c`, []string{`a`, `b;c`}},
+	{`"a";b";c`, []string{`a`, `b;c`}},
+}
+
+func TestSplitList(t *testing.T) {
+	tests := splitlisttests
+	if runtime.GOOS == "windows" {
+		tests = append(tests, winsplitlisttests...)
+	}
+	for _, test := range tests {
+		if l := filepath.SplitList(test.list); !reflect.DeepEqual(l, test.result) {
+			t.Errorf("SplitList(%#q) = %#q, want %#q", test.list, l, test.result)
+		}
+	}
+}
+
+type SplitTest struct {
+	path, dir, file string
+}
+
+var unixsplittests = []SplitTest{
+	{"a/b", "a/", "b"},
+	{"a/b/", "a/b/", ""},
+	{"a/", "a/", ""},
+	{"a", "", "a"},
+	{"/", "/", ""},
+}
+
+var winsplittests = []SplitTest{
+	{`c:`, `c:`, ``},
+	{`c:/`, `c:/`, ``},
+	{`c:/foo`, `c:/`, `foo`},
+	{`c:/foo/bar`, `c:/foo/`, `bar`},
+	{`//host/share`, `//host/share`, ``},
+	{`//host/share/`, `//host/share/`, ``},
+	{`//host/share/foo`, `//host/share/`, `foo`},
+	{`\\host\share`, `\\host\share`, ``},
+	{`\\host\share\`, `\\host\share\`, ``},
+	{`\\host\share\foo`, `\\host\share\`, `foo`},
+}
+
+func TestSplit(t *testing.T) {
+	var splittests []SplitTest
+	splittests = unixsplittests
+	if runtime.GOOS == "windows" {
+		splittests = append(splittests, winsplittests...)
+	}
+	for _, test := range splittests {
+		if d, f := filepath.Split(test.path); d != test.dir || f != test.file {
+			t.Errorf("Split(%q) = %q, %q, want %q, %q", test.path, d, f, test.dir, test.file)
+		}
+	}
+}
+
+type JoinTest struct {
+	elem []string
+	path string
+}
+
+var jointests = []JoinTest{
+	// zero parameters
+	{[]string{}, ""},
+
+	// one parameter
+	{[]string{""}, ""},
+	{[]string{"a"}, "a"},
+
+	// two parameters
+	{[]string{"a", "b"}, "a/b"},
+	{[]string{"a", ""}, "a"},
+	{[]string{"", "b"}, "b"},
+	{[]string{"/", "a"}, "/a"},
+	{[]string{"/", ""}, "/"},
+	{[]string{"a/", "b"}, "a/b"},
+	{[]string{"a/", ""}, "a"},
+	{[]string{"", ""}, ""},
+}
+
+var winjointests = []JoinTest{
+	{[]string{`directory`, `file`}, `directory\file`},
+	{[]string{`C:\Windows\`, `System32`}, `C:\Windows\System32`},
+	{[]string{`C:\Windows\`, ``}, `C:\Windows`},
+	{[]string{`C:\`, `Windows`}, `C:\Windows`},
+	{[]string{`C:`, `Windows`}, `C:\Windows`},
+	{[]string{`\\host\share`, `foo`}, `\\host\share\foo`},
+	{[]string{`//host/share`, `foo/bar`}, `\\host\share\foo\bar`},
+}
+
+// join takes a []string and passes it to Join.
+func join(elem []string, args ...string) string {
+	args = elem
+	return filepath.Join(args...)
+}
+
+func TestJoin(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		jointests = append(jointests, winjointests...)
+	}
+	for _, test := range jointests {
+		if p := join(test.elem); p != filepath.FromSlash(test.path) {
+			t.Errorf("join(%q) = %q, want %q", test.elem, p, test.path)
+		}
+	}
+}
+
+type ExtTest struct {
+	path, ext string
+}
+
+var exttests = []ExtTest{
+	{"path.go", ".go"},
+	{"path.pb.go", ".go"},
+	{"a.dir/b", ""},
+	{"a.dir/b.go", ".go"},
+	{"a.dir/", ""},
+}
+
+func TestExt(t *testing.T) {
+	for _, test := range exttests {
+		if x := filepath.Ext(test.path); x != test.ext {
+			t.Errorf("Ext(%q) = %q, want %q", test.path, x, test.ext)
+		}
+	}
+}
+
+type Node struct {
+	name    string
+	entries []*Node // nil if the entry is a file
+	mark    int
+}
+
+var tree = &Node{
+	"testdata",
+	[]*Node{
+		{"a", nil, 0},
+		{"b", []*Node{}, 0},
+		{"c", nil, 0},
+		{
+			"d",
+			[]*Node{
+				{"x", nil, 0},
+				{"y", []*Node{}, 0},
+				{
+					"z",
+					[]*Node{
+						{"u", nil, 0},
+						{"v", nil, 0},
+					},
+					0,
+				},
+			},
+			0,
+		},
+	},
+	0,
+}
+
+func walkTree(n *Node, path string, f func(path string, n *Node)) {
+	f(path, n)
+	for _, e := range n.entries {
+		walkTree(e, filepath.Join(path, e.name), f)
+	}
+}
+
+func makeTree(t *testing.T) {
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.entries == nil {
+			fd, err := os.Create(path)
+			if err != nil {
+				t.Errorf("makeTree: %v", err)
+				return
+			}
+			fd.Close()
+		} else {
+			os.Mkdir(path, 0770)
+		}
+	})
+}
+
+func markTree(n *Node) { walkTree(n, "", func(path string, n *Node) { n.mark++ }) }
+
+func checkMarks(t *testing.T, report bool) {
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.mark != 1 && report {
+			t.Errorf("node %s mark = %d; expected 1", path, n.mark)
+		}
+		n.mark = 0
+	})
+}
+
+// Assumes that each node name is unique. Good enough for a test.
+// If clear is true, any incoming error is cleared before return. The errors
+// are always accumulated, though.
+func mark(path string, info os.FileInfo, err error, errors *[]error, clear bool) error {
+	if err != nil {
+		*errors = append(*errors, err)
+		if clear {
+			return nil
+		}
+		return err
+	}
+	name := info.Name()
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.name == name {
+			n.mark++
+		}
+	})
+	return nil
+}
+
+func TestWalk(t *testing.T) {
+	makeTree(t)
+	errors := make([]error, 0, 10)
+	clear := true
+	markFn := func(path string, info os.FileInfo, err error) error {
+		return mark(path, info, err, &errors, clear)
+	}
+	// Expect no errors.
+	err := filepath.Walk(tree.name, markFn)
+	if err != nil {
+		t.Fatalf("no error expected, found: %s", err)
+	}
+	if len(errors) != 0 {
+		t.Fatalf("unexpected errors: %s", errors)
+	}
+	checkMarks(t, true)
+	errors = errors[0:0]
+
+	// Test permission errors.  Only possible if we're not root
+	// and only on some file systems (AFS, FAT).  To avoid errors during
+	// all.bash on those file systems, skip during go test -short.
+	if os.Getuid() > 0 && !testing.Short() {
+		// introduce 2 errors: chmod top-level directories to 0
+		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0)
+		os.Chmod(filepath.Join(tree.name, tree.entries[3].name), 0)
+
+		// 3) capture errors, expect two.
+		// mark respective subtrees manually
+		markTree(tree.entries[1])
+		markTree(tree.entries[3])
+		// correct double-marking of directory itself
+		tree.entries[1].mark--
+		tree.entries[3].mark--
+		err := filepath.Walk(tree.name, markFn)
+		if err != nil {
+			t.Fatalf("expected no error return from Walk, got %s", err)
+		}
+		if len(errors) != 2 {
+			t.Errorf("expected 2 errors, got %d: %s", len(errors), errors)
+		}
+		// the inaccessible subtrees were marked manually
+		checkMarks(t, true)
+		errors = errors[0:0]
+
+		// 4) capture errors, stop after first error.
+		// mark respective subtrees manually
+		markTree(tree.entries[1])
+		markTree(tree.entries[3])
+		// correct double-marking of directory itself
+		tree.entries[1].mark--
+		tree.entries[3].mark--
+		clear = false // error will stop processing
+		err = filepath.Walk(tree.name, markFn)
+		if err == nil {
+			t.Fatalf("expected error return from Walk")
+		}
+		if len(errors) != 1 {
+			t.Errorf("expected 1 error, got %d: %s", len(errors), errors)
+		}
+		// the inaccessible subtrees were marked manually
+		checkMarks(t, false)
+		errors = errors[0:0]
+
+		// restore permissions
+		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0770)
+		os.Chmod(filepath.Join(tree.name, tree.entries[3].name), 0770)
+	}
+
+	// cleanup
+	if err := os.RemoveAll(tree.name); err != nil {
+		t.Errorf("removeTree: %v", err)
+	}
+}
+
+func touch(t *testing.T, name string) {
+	f, err := os.Create(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestWalkFileError(t *testing.T) {
+	td, err := ioutil.TempDir("", "walktest")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(td)
+
+	touch(t, filepath.Join(td, "foo"))
+	touch(t, filepath.Join(td, "bar"))
+	dir := filepath.Join(td, "dir")
+	if err := os.MkdirAll(filepath.Join(td, "dir"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	touch(t, filepath.Join(dir, "baz"))
+	touch(t, filepath.Join(dir, "stat-error"))
+	defer func() {
+		*filepath.LstatP = os.Lstat
+	}()
+	statErr := errors.New("some stat error")
+	*filepath.LstatP = func(path string) (os.FileInfo, error) {
+		if strings.HasSuffix(path, "stat-error") {
+			return nil, statErr
+		}
+		return os.Lstat(path)
+	}
+	got := map[string]error{}
+	err = filepath.Walk(td, func(path string, fi os.FileInfo, err error) error {
+		rel, _ := filepath.Rel(td, path)
+		got[filepath.ToSlash(rel)] = err
+		return nil
+	})
+	if err != nil {
+		t.Errorf("Walk error: %v", err)
+	}
+	want := map[string]error{
+		".":              nil,
+		"foo":            nil,
+		"bar":            nil,
+		"dir":            nil,
+		"dir/baz":        nil,
+		"dir/stat-error": statErr,
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Walked %#v; want %#v", got, want)
+	}
+}
+
+var basetests = []PathTest{
+	{"", "."},
+	{".", "."},
+	{"/.", "."},
+	{"/", "/"},
+	{"////", "/"},
+	{"x/", "x"},
+	{"abc", "abc"},
+	{"abc/def", "def"},
+	{"a/b/.x", ".x"},
+	{"a/b/c.", "c."},
+	{"a/b/c.x", "c.x"},
+}
+
+var winbasetests = []PathTest{
+	{`c:\`, `\`},
+	{`c:.`, `.`},
+	{`c:\a\b`, `b`},
+	{`c:a\b`, `b`},
+	{`c:a\b\c`, `c`},
+	{`\\host\share\`, `\`},
+	{`\\host\share\a`, `a`},
+	{`\\host\share\a\b`, `b`},
+}
+
+func TestBase(t *testing.T) {
+	tests := basetests
+	if runtime.GOOS == "windows" {
+		// make unix tests work on windows
+		for i := range tests {
+			tests[i].result = filepath.Clean(tests[i].result)
+		}
+		// add windows specific tests
+		tests = append(tests, winbasetests...)
+	}
+	for _, test := range tests {
+		if s := filepath.Base(test.path); s != test.result {
+			t.Errorf("Base(%q) = %q, want %q", test.path, s, test.result)
+		}
+	}
+}
+
+var dirtests = []PathTest{
+	{"", "."},
+	{".", "."},
+	{"/.", "/"},
+	{"/", "/"},
+	{"////", "/"},
+	{"/foo", "/"},
+	{"x/", "x"},
+	{"abc", "."},
+	{"abc/def", "abc"},
+	{"a/b/.x", "a/b"},
+	{"a/b/c.", "a/b"},
+	{"a/b/c.x", "a/b"},
+}
+
+var windirtests = []PathTest{
+	{`c:\`, `c:\`},
+	{`c:.`, `c:.`},
+	{`c:\a\b`, `c:\a`},
+	{`c:a\b`, `c:a`},
+	{`c:a\b\c`, `c:a\b`},
+	{`\\host\share\`, `\\host\share\`},
+	{`\\host\share\a`, `\\host\share\`},
+	{`\\host\share\a\b`, `\\host\share\a`},
+}
+
+func TestDir(t *testing.T) {
+	tests := dirtests
+	if runtime.GOOS == "windows" {
+		// make unix tests work on windows
+		for i := range tests {
+			tests[i].result = filepath.Clean(tests[i].result)
+		}
+		// add windows specific tests
+		tests = append(tests, windirtests...)
+	}
+	for _, test := range tests {
+		if s := filepath.Dir(test.path); s != test.result {
+			t.Errorf("Dir(%q) = %q, want %q", test.path, s, test.result)
+		}
+	}
+}
+
+type IsAbsTest struct {
+	path  string
+	isAbs bool
+}
+
+var isabstests = []IsAbsTest{
+	{"", false},
+	{"/", true},
+	{"/usr/bin/gcc", true},
+	{"..", false},
+	{"/a/../bb", true},
+	{".", false},
+	{"./", false},
+	{"lala", false},
+}
+
+var winisabstests = []IsAbsTest{
+	{`C:\`, true},
+	{`c\`, false},
+	{`c::`, false},
+	{`c:`, false},
+	{`/`, false},
+	{`\`, false},
+	{`\Windows`, false},
+	{`c:a\b`, false},
+	{`c:\a\b`, true},
+	{`c:/a/b`, true},
+	{`\\host\share\foo`, true},
+	{`//host/share/foo/bar`, true},
+}
+
+func TestIsAbs(t *testing.T) {
+	var tests []IsAbsTest
+	if runtime.GOOS == "windows" {
+		tests = append(tests, winisabstests...)
+		// All non-windows tests should fail, because they have no volume letter.
+		for _, test := range isabstests {
+			tests = append(tests, IsAbsTest{test.path, false})
+		}
+		// All non-windows test should work as intended if prefixed with volume letter.
+		for _, test := range isabstests {
+			tests = append(tests, IsAbsTest{"c:" + test.path, test.isAbs})
+		}
+	} else {
+		tests = isabstests
+	}
+
+	for _, test := range tests {
+		if r := filepath.IsAbs(test.path); r != test.isAbs {
+			t.Errorf("IsAbs(%q) = %v, want %v", test.path, r, test.isAbs)
+		}
+	}
+}
+
+type EvalSymlinksTest struct {
+	// If dest is empty, the path is created; otherwise the dest is symlinked to the path.
+	path, dest string
+}
+
+var EvalSymlinksTestDirs = []EvalSymlinksTest{
+	{"test", ""},
+	{"test/dir", ""},
+	{"test/dir/link3", "../../"},
+	{"test/link1", "../test"},
+	{"test/link2", "dir"},
+	{"test/linkabs", "/"},
+}
+
+var EvalSymlinksTests = []EvalSymlinksTest{
+	{"test", "test"},
+	{"test/dir", "test/dir"},
+	{"test/dir/../..", "."},
+	{"test/link1", "test"},
+	{"test/link2", "test/dir"},
+	{"test/link1/dir", "test/dir"},
+	{"test/link2/..", "test"},
+	{"test/dir/link3", "."},
+	{"test/link2/link3/test", "test"},
+	{"test/linkabs", "/"},
+}
+
+var EvalSymlinksAbsWindowsTests = []EvalSymlinksTest{
+	{`c:\`, `c:\`},
+}
+
+// simpleJoin builds a file name from the directory and path.
+// It does not use Join because we don't want ".." to be evaluated.
+func simpleJoin(dir, path string) string {
+	return dir + string(filepath.Separator) + path
+}
+
+func TestEvalSymlinks(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9":
+		t.Skipf("skipping on %s", runtime.GOOS)
+	}
+
+	tmpDir, err := ioutil.TempDir("", "evalsymlink")
+	if err != nil {
+		t.Fatal("creating temp dir:", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// /tmp may itself be a symlink! Avoid the confusion, although
+	// it means trusting the thing we're testing.
+	tmpDir, err = filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal("eval symlink for tmp dir:", err)
+	}
+
+	// Create the symlink farm using relative paths.
+	for _, d := range EvalSymlinksTestDirs {
+		var err error
+		path := simpleJoin(tmpDir, d.path)
+		if d.dest == "" {
+			err = os.Mkdir(path, 0755)
+		} else {
+			if supportsSymlinks {
+				err = os.Symlink(d.dest, path)
+			}
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	var tests []EvalSymlinksTest
+	if supportsSymlinks {
+		tests = EvalSymlinksTests
+	} else {
+		for _, d := range EvalSymlinksTests {
+			if d.path == d.dest {
+				// will test only real files and directories
+				tests = append(tests, d)
+				// test "canonical" names
+				d2 := EvalSymlinksTest{
+					path: strings.ToUpper(d.path),
+					dest: d.dest,
+				}
+				tests = append(tests, d2)
+			}
+		}
+	}
+
+	// Evaluate the symlink farm.
+	for _, d := range tests {
+		path := simpleJoin(tmpDir, d.path)
+		dest := simpleJoin(tmpDir, d.dest)
+		if filepath.IsAbs(d.dest) || os.IsPathSeparator(d.dest[0]) {
+			dest = d.dest
+		}
+		if p, err := filepath.EvalSymlinks(path); err != nil {
+			t.Errorf("EvalSymlinks(%q) error: %v", d.path, err)
+		} else if filepath.Clean(p) != filepath.Clean(dest) {
+			t.Errorf("Clean(%q)=%q, want %q", path, p, dest)
+		}
+	}
+}
+
+// Test directories relative to temporary directory.
+// The tests are run in absTestDirs[0].
+var absTestDirs = []string{
+	"a",
+	"a/b",
+	"a/b/c",
+}
+
+// Test paths relative to temporary directory. $ expands to the directory.
+// The tests are run in absTestDirs[0].
+// We create absTestDirs first.
+var absTests = []string{
+	".",
+	"b",
+	"../a",
+	"../a/b",
+	"../a/b/./c/../../.././a",
+	"$",
+	"$/.",
+	"$/a/../a/b",
+	"$/a/b/c/../../.././a",
+}
+
+func TestAbs(t *testing.T) {
+	root, err := ioutil.TempDir("", "TestAbs")
+	if err != nil {
+		t.Fatal("TempDir failed: ", err)
+	}
+	defer os.RemoveAll(root)
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal("getwd failed: ", err)
+	}
+	err = os.Chdir(root)
+	if err != nil {
+		t.Fatal("chdir failed: ", err)
+	}
+	defer os.Chdir(wd)
+
+	for _, dir := range absTestDirs {
+		err = os.Mkdir(dir, 0777)
+		if err != nil {
+			t.Fatal("Mkdir failed: ", err)
+		}
+	}
+
+	if runtime.GOOS == "windows" {
+		vol := filepath.VolumeName(root)
+		var extra []string
+		for _, path := range absTests {
+			if strings.Index(path, "$") != -1 {
+				continue
+			}
+			path = vol + path
+			extra = append(extra, path)
+		}
+		absTests = append(absTests, extra...)
+	}
+
+	err = os.Chdir(absTestDirs[0])
+	if err != nil {
+		t.Fatal("chdir failed: ", err)
+	}
+
+	for _, path := range absTests {
+		path = strings.Replace(path, "$", root, -1)
+		info, err := os.Stat(path)
+		if err != nil {
+			t.Errorf("%s: %s", path, err)
+			continue
+		}
+
+		abspath, err := filepath.Abs(path)
+		if err != nil {
+			t.Errorf("Abs(%q) error: %v", path, err)
+			continue
+		}
+		absinfo, err := os.Stat(abspath)
+		if err != nil || !os.SameFile(absinfo, info) {
+			t.Errorf("Abs(%q)=%q, not the same file", path, abspath)
+		}
+		if !filepath.IsAbs(abspath) {
+			t.Errorf("Abs(%q)=%q, not an absolute path", path, abspath)
+		}
+		if filepath.IsAbs(path) && abspath != filepath.Clean(path) {
+			t.Errorf("Abs(%q)=%q, isn't clean", path, abspath)
+		}
+	}
+}
+
+type RelTests struct {
+	root, path, want string
+}
+
+var reltests = []RelTests{
+	{"a/b", "a/b", "."},
+	{"a/b/.", "a/b", "."},
+	{"a/b", "a/b/.", "."},
+	{"./a/b", "a/b", "."},
+	{"a/b", "./a/b", "."},
+	{"ab/cd", "ab/cde", "../cde"},
+	{"ab/cd", "ab/c", "../c"},
+	{"a/b", "a/b/c/d", "c/d"},
+	{"a/b", "a/b/../c", "../c"},
+	{"a/b/../c", "a/b", "../b"},
+	{"a/b/c", "a/c/d", "../../c/d"},
+	{"a/b", "c/d", "../../c/d"},
+	{"a/b/c/d", "a/b", "../.."},
+	{"a/b/c/d", "a/b/", "../.."},
+	{"a/b/c/d/", "a/b", "../.."},
+	{"a/b/c/d/", "a/b/", "../.."},
+	{"../../a/b", "../../a/b/c/d", "c/d"},
+	{"/a/b", "/a/b", "."},
+	{"/a/b/.", "/a/b", "."},
+	{"/a/b", "/a/b/.", "."},
+	{"/ab/cd", "/ab/cde", "../cde"},
+	{"/ab/cd", "/ab/c", "../c"},
+	{"/a/b", "/a/b/c/d", "c/d"},
+	{"/a/b", "/a/b/../c", "../c"},
+	{"/a/b/../c", "/a/b", "../b"},
+	{"/a/b/c", "/a/c/d", "../../c/d"},
+	{"/a/b", "/c/d", "../../c/d"},
+	{"/a/b/c/d", "/a/b", "../.."},
+	{"/a/b/c/d", "/a/b/", "../.."},
+	{"/a/b/c/d/", "/a/b", "../.."},
+	{"/a/b/c/d/", "/a/b/", "../.."},
+	{"/../../a/b", "/../../a/b/c/d", "c/d"},
+	{".", "a/b", "a/b"},
+	{".", "..", ".."},
+
+	// can't do purely lexically
+	{"..", ".", "err"},
+	{"..", "a", "err"},
+	{"../..", "..", "err"},
+	{"a", "/a", "err"},
+	{"/a", "a", "err"},
+}
+
+var winreltests = []RelTests{
+	{`C:a\b\c`, `C:a/b/d`, `..\d`},
+	{`C:\`, `D:\`, `err`},
+	{`C:`, `D:`, `err`},
+}
+
+func TestRel(t *testing.T) {
+	tests := append([]RelTests{}, reltests...)
+	if runtime.GOOS == "windows" {
+		for i := range tests {
+			tests[i].want = filepath.FromSlash(tests[i].want)
+		}
+		tests = append(tests, winreltests...)
+	}
+	for _, test := range tests {
+		got, err := filepath.Rel(test.root, test.path)
+		if test.want == "err" {
+			if err == nil {
+				t.Errorf("Rel(%q, %q)=%q, want error", test.root, test.path, got)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("Rel(%q, %q): want %q, got error: %s", test.root, test.path, test.want, err)
+		}
+		if got != test.want {
+			t.Errorf("Rel(%q, %q)=%q, want %q", test.root, test.path, got, test.want)
+		}
+	}
+}
+
+type VolumeNameTest struct {
+	path string
+	vol  string
+}
+
+var volumenametests = []VolumeNameTest{
+	{`c:/foo/bar`, `c:`},
+	{`c:`, `c:`},
+	{`2:`, ``},
+	{``, ``},
+	{`\\\host`, ``},
+	{`\\\host\`, ``},
+	{`\\\host\share`, ``},
+	{`\\\host\\share`, ``},
+	{`\\host`, ``},
+	{`//host`, ``},
+	{`\\host\`, ``},
+	{`//host/`, ``},
+	{`\\host\share`, `\\host\share`},
+	{`//host/share`, `//host/share`},
+	{`\\host\share\`, `\\host\share`},
+	{`//host/share/`, `//host/share`},
+	{`\\host\share\foo`, `\\host\share`},
+	{`//host/share/foo`, `//host/share`},
+	{`\\host\share\\foo\\\bar\\\\baz`, `\\host\share`},
+	{`//host/share//foo///bar////baz`, `//host/share`},
+	{`\\host\share\foo\..\bar`, `\\host\share`},
+	{`//host/share/foo/../bar`, `//host/share`},
+}
+
+func TestVolumeName(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		return
+	}
+	for _, v := range volumenametests {
+		if vol := filepath.VolumeName(v.path); vol != v.vol {
+			t.Errorf("VolumeName(%q)=%q, want %q", v.path, vol, v.vol)
+		}
+	}
+}
+
+func TestDriveLetterInEvalSymlinks(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		return
+	}
+	wd, _ := os.Getwd()
+	if len(wd) < 3 {
+		t.Errorf("Current directory path %q is too short", wd)
+	}
+	lp := strings.ToLower(wd)
+	up := strings.ToUpper(wd)
+	flp, err := filepath.EvalSymlinks(lp)
+	if err != nil {
+		t.Fatalf("EvalSymlinks(%q) failed: %q", lp, err)
+	}
+	fup, err := filepath.EvalSymlinks(up)
+	if err != nil {
+		t.Fatalf("EvalSymlinks(%q) failed: %q", up, err)
+	}
+	if flp != fup {
+		t.Errorf("Results of EvalSymlinks do not match: %q and %q", flp, fup)
+	}
+}
+
+func TestBug3486(t *testing.T) { // http://code.google.com/p/go/issues/detail?id=3486
+	root, err := filepath.EvalSymlinks(runtime.GOROOT() + "/test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	bugs := filepath.Join(root, "bugs")
+	ken := filepath.Join(root, "ken")
+	seenBugs := false
+	seenKen := false
+	filepath.Walk(root, func(pth string, info os.FileInfo, err error) error {
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		switch pth {
+		case bugs:
+			seenBugs = true
+			return filepath.SkipDir
+		case ken:
+			if !seenBugs {
+				t.Fatal("filepath.Walk out of order - ken before bugs")
+			}
+			seenKen = true
+		}
+		return nil
+	})
+	if !seenKen {
+		t.Fatalf("%q not seen", ken)
+	}
+}
diff --git a/src/path/filepath/path_unix.go b/src/path/filepath/path_unix.go
new file mode 100644
index 000000000..4e7d0d1b4
--- /dev/null
+++ b/src/path/filepath/path_unix.go
@@ -0,0 +1,36 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package filepath
+
+import "strings"
+
+// IsAbs returns true if the path is absolute.
+func IsAbs(path string) bool {
+	return strings.HasPrefix(path, "/")
+}
+
+// volumeNameLen returns length of the leading volume name on Windows.
+// It returns 0 elsewhere.
+func volumeNameLen(path string) int {
+	return 0
+}
+
+// HasPrefix exists for historical compatibility and should not be used.
+func HasPrefix(p, prefix string) bool {
+	return strings.HasPrefix(p, prefix)
+}
+
+func splitList(path string) []string {
+	if path == "" {
+		return []string{}
+	}
+	return strings.Split(path, string(ListSeparator))
+}
+
+func abs(path string) (string, error) {
+	return unixAbs(path)
+}
diff --git a/src/path/filepath/path_windows.go b/src/path/filepath/path_windows.go
new file mode 100644
index 000000000..ec50f6b26
--- /dev/null
+++ b/src/path/filepath/path_windows.go
@@ -0,0 +1,110 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath
+
+import (
+	"strings"
+	"syscall"
+)
+
+func isSlash(c uint8) bool {
+	return c == '\\' || c == '/'
+}
+
+// IsAbs returns true if the path is absolute.
+func IsAbs(path string) (b bool) {
+	l := volumeNameLen(path)
+	if l == 0 {
+		return false
+	}
+	path = path[l:]
+	if path == "" {
+		return false
+	}
+	return isSlash(path[0])
+}
+
+// volumeNameLen returns length of the leading volume name on Windows.
+// It returns 0 elsewhere.
+func volumeNameLen(path string) int {
+	if len(path) < 2 {
+		return 0
+	}
+	// with drive letter
+	c := path[0]
+	if path[1] == ':' && ('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
+		return 2
+	}
+	// is it UNC
+	if l := len(path); l >= 5 && isSlash(path[0]) && isSlash(path[1]) &&
+		!isSlash(path[2]) && path[2] != '.' {
+		// first, leading `\\` and next shouldn't be `\`. its server name.
+		for n := 3; n < l-1; n++ {
+			// second, next '\' shouldn't be repeated.
+			if isSlash(path[n]) {
+				n++
+				// third, following something characters. its share name.
+				if !isSlash(path[n]) {
+					if path[n] == '.' {
+						break
+					}
+					for ; n < l; n++ {
+						if isSlash(path[n]) {
+							break
+						}
+					}
+					return n
+				}
+				break
+			}
+		}
+	}
+	return 0
+}
+
+// HasPrefix exists for historical compatibility and should not be used.
+func HasPrefix(p, prefix string) bool {
+	if strings.HasPrefix(p, prefix) {
+		return true
+	}
+	return strings.HasPrefix(strings.ToLower(p), strings.ToLower(prefix))
+}
+
+func splitList(path string) []string {
+	// The same implementation is used in LookPath in os/exec;
+	// consider changing os/exec when changing this.
+
+	if path == "" {
+		return []string{}
+	}
+
+	// Split path, respecting but preserving quotes.
+	list := []string{}
+	start := 0
+	quo := false
+	for i := 0; i < len(path); i++ {
+		switch c := path[i]; {
+		case c == '"':
+			quo = !quo
+		case c == ListSeparator && !quo:
+			list = append(list, path[start:i])
+			start = i + 1
+		}
+	}
+	list = append(list, path[start:])
+
+	// Remove quotes.
+	for i, s := range list {
+		if strings.Contains(s, `"`) {
+			list[i] = strings.Replace(s, `"`, ``, -1)
+		}
+	}
+
+	return list
+}
+
+func abs(path string) (string, error) {
+	return syscall.FullPath(path)
+}
diff --git a/src/path/filepath/path_windows_test.go b/src/path/filepath/path_windows_test.go
new file mode 100644
index 000000000..100cf30a4
--- /dev/null
+++ b/src/path/filepath/path_windows_test.go
@@ -0,0 +1,113 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath_test
+
+import (
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"reflect"
+	"syscall"
+	"testing"
+)
+
+func init() {
+	tmpdir, err := ioutil.TempDir("", "symtest")
+	if err != nil {
+		panic("failed to create temp directory: " + err.Error())
+	}
+	defer os.RemoveAll(tmpdir)
+
+	err = os.Symlink("target", filepath.Join(tmpdir, "symlink"))
+	if err == nil {
+		return
+	}
+
+	err = err.(*os.LinkError).Err
+	switch err {
+	case syscall.EWINDOWS, syscall.ERROR_PRIVILEGE_NOT_HELD:
+		supportsSymlinks = false
+	}
+}
+
+func TestWinSplitListTestsAreValid(t *testing.T) {
+	comspec := os.Getenv("ComSpec")
+	if comspec == "" {
+		t.Fatal("%ComSpec% must be set")
+	}
+
+	for ti, tt := range winsplitlisttests {
+		testWinSplitListTestIsValid(t, ti, tt, comspec)
+	}
+}
+
+func testWinSplitListTestIsValid(t *testing.T, ti int, tt SplitListTest,
+	comspec string) {
+
+	const (
+		cmdfile             = `printdir.cmd`
+		perm    os.FileMode = 0700
+	)
+
+	tmp, err := ioutil.TempDir("", "testWinSplitListTestIsValid")
+	if err != nil {
+		t.Fatalf("TempDir failed: %v", err)
+	}
+	defer os.RemoveAll(tmp)
+
+	for i, d := range tt.result {
+		if d == "" {
+			continue
+		}
+		if cd := filepath.Clean(d); filepath.VolumeName(cd) != "" ||
+			cd[0] == '\\' || cd == ".." || (len(cd) >= 3 && cd[0:3] == `..\`) {
+			t.Errorf("%d,%d: %#q refers outside working directory", ti, i, d)
+			return
+		}
+		dd := filepath.Join(tmp, d)
+		if _, err := os.Stat(dd); err == nil {
+			t.Errorf("%d,%d: %#q already exists", ti, i, d)
+			return
+		}
+		if err = os.MkdirAll(dd, perm); err != nil {
+			t.Errorf("%d,%d: MkdirAll(%#q) failed: %v", ti, i, dd, err)
+			return
+		}
+		fn, data := filepath.Join(dd, cmdfile), []byte("@echo "+d+"\r\n")
+		if err = ioutil.WriteFile(fn, data, perm); err != nil {
+			t.Errorf("%d,%d: WriteFile(%#q) failed: %v", ti, i, fn, err)
+			return
+		}
+	}
+
+	for i, d := range tt.result {
+		if d == "" {
+			continue
+		}
+		exp := []byte(d + "\r\n")
+		cmd := &exec.Cmd{
+			Path: comspec,
+			Args: []string{`/c`, cmdfile},
+			Env:  []string{`Path=` + tt.list},
+			Dir:  tmp,
+		}
+		out, err := cmd.CombinedOutput()
+		switch {
+		case err != nil:
+			t.Errorf("%d,%d: execution error %v\n%q", ti, i, err, out)
+			return
+		case !reflect.DeepEqual(out, exp):
+			t.Errorf("%d,%d: expected %#q, got %#q", ti, i, exp, out)
+			return
+		default:
+			// unshadow cmdfile in next directory
+			err = os.Remove(filepath.Join(tmp, d, cmdfile))
+			if err != nil {
+				t.Fatalf("Remove test command failed: %v", err)
+			}
+		}
+	}
+}
diff --git a/src/path/filepath/symlink.go b/src/path/filepath/symlink.go
new file mode 100644
index 000000000..df0a9e0c2
--- /dev/null
+++ b/src/path/filepath/symlink.go
@@ -0,0 +1,72 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath
+
+import (
+	"bytes"
+	"errors"
+	"os"
+)
+
+const utf8RuneSelf = 0x80
+
+func walkSymlinks(path string) (string, error) {
+	const maxIter = 255
+	originalPath := path
+	// consume path by taking each frontmost path element,
+	// expanding it if it's a symlink, and appending it to b
+	var b bytes.Buffer
+	for n := 0; path != ""; n++ {
+		if n > maxIter {
+			return "", errors.New("EvalSymlinks: too many links in " + originalPath)
+		}
+
+		// find next path component, p
+		var i = -1
+		for j, c := range path {
+			if c < utf8RuneSelf && os.IsPathSeparator(uint8(c)) {
+				i = j
+				break
+			}
+		}
+		var p string
+		if i == -1 {
+			p, path = path, ""
+		} else {
+			p, path = path[:i], path[i+1:]
+		}
+
+		if p == "" {
+			if b.Len() == 0 {
+				// must be absolute path
+				b.WriteRune(Separator)
+			}
+			continue
+		}
+
+		fi, err := os.Lstat(b.String() + p)
+		if err != nil {
+			return "", err
+		}
+		if fi.Mode()&os.ModeSymlink == 0 {
+			b.WriteString(p)
+			if path != "" || (b.Len() == 2 && len(p) == 2 && p[1] == ':') {
+				b.WriteRune(Separator)
+			}
+			continue
+		}
+
+		// it's a symlink, put it at the front of path
+		dest, err := os.Readlink(b.String() + p)
+		if err != nil {
+			return "", err
+		}
+		if IsAbs(dest) || os.IsPathSeparator(dest[0]) {
+			b.Reset()
+		}
+		path = dest + string(Separator) + path
+	}
+	return Clean(b.String()), nil
+}
diff --git a/src/path/filepath/symlink_unix.go b/src/path/filepath/symlink_unix.go
new file mode 100644
index 000000000..d20e63a98
--- /dev/null
+++ b/src/path/filepath/symlink_unix.go
@@ -0,0 +1,7 @@
+// +build !windows
+
+package filepath
+
+func evalSymlinks(path string) (string, error) {
+	return walkSymlinks(path)
+}
diff --git a/src/path/filepath/symlink_windows.go b/src/path/filepath/symlink_windows.go
new file mode 100644
index 000000000..327c2c89a
--- /dev/null
+++ b/src/path/filepath/symlink_windows.go
@@ -0,0 +1,74 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package filepath
+
+import (
+	"syscall"
+)
+
+func toShort(path string) (string, error) {
+	p, err := syscall.UTF16FromString(path)
+	if err != nil {
+		return "", err
+	}
+	b := p // GetShortPathName says we can reuse buffer
+	n, err := syscall.GetShortPathName(&p[0], &b[0], uint32(len(b)))
+	if err != nil {
+		return "", err
+	}
+	if n > uint32(len(b)) {
+		b = make([]uint16, n)
+		n, err = syscall.GetShortPathName(&p[0], &b[0], uint32(len(b)))
+		if err != nil {
+			return "", err
+		}
+	}
+	return syscall.UTF16ToString(b), nil
+}
+
+func toLong(path string) (string, error) {
+	p, err := syscall.UTF16FromString(path)
+	if err != nil {
+		return "", err
+	}
+	b := p // GetLongPathName says we can reuse buffer
+	n, err := syscall.GetLongPathName(&p[0], &b[0], uint32(len(b)))
+	if err != nil {
+		return "", err
+	}
+	if n > uint32(len(b)) {
+		b = make([]uint16, n)
+		n, err = syscall.GetLongPathName(&p[0], &b[0], uint32(len(b)))
+		if err != nil {
+			return "", err
+		}
+	}
+	b = b[:n]
+	return syscall.UTF16ToString(b), nil
+}
+
+func evalSymlinks(path string) (string, error) {
+	path, err := walkSymlinks(path)
+	if err != nil {
+		return "", err
+	}
+
+	p, err := toShort(path)
+	if err != nil {
+		return "", err
+	}
+	p, err = toLong(p)
+	if err != nil {
+		return "", err
+	}
+	// syscall.GetLongPathName does not change the case of the drive letter,
+	// but the result of EvalSymlinks must be unique, so we have
+	// EvalSymlinks(`c:\a`) == EvalSymlinks(`C:\a`).
+	// Make drive letter upper case.
+	if len(p) >= 2 && p[1] == ':' && 'a' <= p[0] && p[0] <= 'z' {
+		p = string(p[0]+'A'-'a') + p[1:]
+	}
+	return Clean(p), nil
+}
diff --git a/src/path/match.go b/src/path/match.go
new file mode 100644
index 000000000..8154bf602
--- /dev/null
+++ b/src/path/match.go
@@ -0,0 +1,209 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package path
+
+import (
+	"errors"
+	"strings"
+	"unicode/utf8"
+)
+
+// ErrBadPattern indicates a globbing pattern was malformed.
+var ErrBadPattern = errors.New("syntax error in pattern")
+
+// Match returns true if name matches the shell file name pattern.
+// The pattern syntax is:
+//
+//	pattern:
+//		{ term }
+//	term:
+//		'*'         matches any sequence of non-/ characters
+//		'?'         matches any single non-/ character
+//		'[' [ '^' ] { character-range } ']'
+//		            character class (must be non-empty)
+//		c           matches character c (c != '*', '?', '\\', '[')
+//		'\\' c      matches character c
+//
+//	character-range:
+//		c           matches character c (c != '\\', '-', ']')
+//		'\\' c      matches character c
+//		lo '-' hi   matches character c for lo <= c <= hi
+//
+// Match requires pattern to match all of name, not just a substring.
+// The only possible returned error is ErrBadPattern, when pattern
+// is malformed.
+//
+func Match(pattern, name string) (matched bool, err error) {
+Pattern:
+	for len(pattern) > 0 {
+		var star bool
+		var chunk string
+		star, chunk, pattern = scanChunk(pattern)
+		if star && chunk == "" {
+			// Trailing * matches rest of string unless it has a /.
+			return strings.Index(name, "/") < 0, nil
+		}
+		// Look for match at current position.
+		t, ok, err := matchChunk(chunk, name)
+		// if we're the last chunk, make sure we've exhausted the name
+		// otherwise we'll give a false result even if we could still match
+		// using the star
+		if ok && (len(t) == 0 || len(pattern) > 0) {
+			name = t
+			continue
+		}
+		if err != nil {
+			return false, err
+		}
+		if star {
+			// Look for match skipping i+1 bytes.
+			// Cannot skip /.
+			for i := 0; i < len(name) && name[i] != '/'; i++ {
+				t, ok, err := matchChunk(chunk, name[i+1:])
+				if ok {
+					// if we're the last chunk, make sure we exhausted the name
+					if len(pattern) == 0 && len(t) > 0 {
+						continue
+					}
+					name = t
+					continue Pattern
+				}
+				if err != nil {
+					return false, err
+				}
+			}
+		}
+		return false, nil
+	}
+	return len(name) == 0, nil
+}
+
+// scanChunk gets the next segment of pattern, which is a non-star string
+// possibly preceded by a star.
+func scanChunk(pattern string) (star bool, chunk, rest string) {
+	for len(pattern) > 0 && pattern[0] == '*' {
+		pattern = pattern[1:]
+		star = true
+	}
+	inrange := false
+	var i int
+Scan:
+	for i = 0; i < len(pattern); i++ {
+		switch pattern[i] {
+		case '\\':
+			// error check handled in matchChunk: bad pattern.
+			if i+1 < len(pattern) {
+				i++
+			}
+		case '[':
+			inrange = true
+		case ']':
+			inrange = false
+		case '*':
+			if !inrange {
+				break Scan
+			}
+		}
+	}
+	return star, pattern[0:i], pattern[i:]
+}
+
+// matchChunk checks whether chunk matches the beginning of s.
+// If so, it returns the remainder of s (after the match).
+// Chunk is all single-character operators: literals, char classes, and ?.
+func matchChunk(chunk, s string) (rest string, ok bool, err error) {
+	for len(chunk) > 0 {
+		if len(s) == 0 {
+			return
+		}
+		switch chunk[0] {
+		case '[':
+			// character class
+			r, n := utf8.DecodeRuneInString(s)
+			s = s[n:]
+			chunk = chunk[1:]
+			// possibly negated
+			notNegated := true
+			if len(chunk) > 0 && chunk[0] == '^' {
+				notNegated = false
+				chunk = chunk[1:]
+			}
+			// parse all ranges
+			match := false
+			nrange := 0
+			for {
+				if len(chunk) > 0 && chunk[0] == ']' && nrange > 0 {
+					chunk = chunk[1:]
+					break
+				}
+				var lo, hi rune
+				if lo, chunk, err = getEsc(chunk); err != nil {
+					return
+				}
+				hi = lo
+				if chunk[0] == '-' {
+					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
+						return
+					}
+				}
+				if lo <= r && r <= hi {
+					match = true
+				}
+				nrange++
+			}
+			if match != notNegated {
+				return
+			}
+
+		case '?':
+			if s[0] == '/' {
+				return
+			}
+			_, n := utf8.DecodeRuneInString(s)
+			s = s[n:]
+			chunk = chunk[1:]
+
+		case '\\':
+			chunk = chunk[1:]
+			if len(chunk) == 0 {
+				err = ErrBadPattern
+				return
+			}
+			fallthrough
+
+		default:
+			if chunk[0] != s[0] {
+				return
+			}
+			s = s[1:]
+			chunk = chunk[1:]
+		}
+	}
+	return s, true, nil
+}
+
+// getEsc gets a possibly-escaped character from chunk, for a character class.
+func getEsc(chunk string) (r rune, nchunk string, err error) {
+	if len(chunk) == 0 || chunk[0] == '-' || chunk[0] == ']' {
+		err = ErrBadPattern
+		return
+	}
+	if chunk[0] == '\\' {
+		chunk = chunk[1:]
+		if len(chunk) == 0 {
+			err = ErrBadPattern
+			return
+		}
+	}
+	r, n := utf8.DecodeRuneInString(chunk)
+	if r == utf8.RuneError && n == 1 {
+		err = ErrBadPattern
+	}
+	nchunk = chunk[n:]
+	if len(nchunk) == 0 {
+		err = ErrBadPattern
+	}
+	return
+}
diff --git a/src/path/match_test.go b/src/path/match_test.go
new file mode 100644
index 000000000..6b0676f81
--- /dev/null
+++ b/src/path/match_test.go
@@ -0,0 +1,79 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package path
+
+import "testing"
+
+type MatchTest struct {
+	pattern, s string
+	match      bool
+	err        error
+}
+
+var matchTests = []MatchTest{
+	{"abc", "abc", true, nil},
+	{"*", "abc", true, nil},
+	{"*c", "abc", true, nil},
+	{"a*", "a", true, nil},
+	{"a*", "abc", true, nil},
+	{"a*", "ab/c", false, nil},
+	{"a*/b", "abc/b", true, nil},
+	{"a*/b", "a/c/b", false, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxe/f", true, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxexxx/f", true, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxe/xxx/f", false, nil},
+	{"a*b*c*d*e*/f", "axbxcxdxexxx/fff", false, nil},
+	{"a*b?c*x", "abxbbxdbxebxczzx", true, nil},
+	{"a*b?c*x", "abxbbxdbxebxczzy", false, nil},
+	{"ab[c]", "abc", true, nil},
+	{"ab[b-d]", "abc", true, nil},
+	{"ab[e-g]", "abc", false, nil},
+	{"ab[^c]", "abc", false, nil},
+	{"ab[^b-d]", "abc", false, nil},
+	{"ab[^e-g]", "abc", true, nil},
+	{"a\\*b", "a*b", true, nil},
+	{"a\\*b", "ab", false, nil},
+	{"a?b", "a☺b", true, nil},
+	{"a[^a]b", "a☺b", true, nil},
+	{"a???b", "a☺b", false, nil},
+	{"a[^a][^a][^a]b", "a☺b", false, nil},
+	{"[a-ζ]*", "α", true, nil},
+	{"*[a-ζ]", "A", false, nil},
+	{"a?b", "a/b", false, nil},
+	{"a*b", "a/b", false, nil},
+	{"[\\]a]", "]", true, nil},
+	{"[\\-]", "-", true, nil},
+	{"[x\\-]", "x", true, nil},
+	{"[x\\-]", "-", true, nil},
+	{"[x\\-]", "z", false, nil},
+	{"[\\-x]", "x", true, nil},
+	{"[\\-x]", "-", true, nil},
+	{"[\\-x]", "a", false, nil},
+	{"[]a]", "]", false, ErrBadPattern},
+	{"[-]", "-", false, ErrBadPattern},
+	{"[x-]", "x", false, ErrBadPattern},
+	{"[x-]", "-", false, ErrBadPattern},
+	{"[x-]", "z", false, ErrBadPattern},
+	{"[-x]", "x", false, ErrBadPattern},
+	{"[-x]", "-", false, ErrBadPattern},
+	{"[-x]", "a", false, ErrBadPattern},
+	{"\\", "a", false, ErrBadPattern},
+	{"[a-b-c]", "a", false, ErrBadPattern},
+	{"[", "a", false, ErrBadPattern},
+	{"[^", "a", false, ErrBadPattern},
+	{"[^bc", "a", false, ErrBadPattern},
+	{"a[", "a", false, nil},
+	{"a[", "ab", false, ErrBadPattern},
+	{"*x", "xxx", true, nil},
+}
+
+func TestMatch(t *testing.T) {
+	for _, tt := range matchTests {
+		ok, err := Match(tt.pattern, tt.s)
+		if ok != tt.match || err != tt.err {
+			t.Errorf("Match(%#q, %#q) = %v, %v want %v, nil", tt.pattern, tt.s, ok, err, tt.match)
+		}
+	}
+}
diff --git a/src/path/path.go b/src/path/path.go
new file mode 100644
index 000000000..98a6d5292
--- /dev/null
+++ b/src/path/path.go
@@ -0,0 +1,210 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package path implements utility routines for manipulating slash-separated
+// paths.
+package path
+
+import (
+	"strings"
+)
+
+// A lazybuf is a lazily constructed path buffer.
+// It supports append, reading previously appended bytes,
+// and retrieving the final string. It does not allocate a buffer
+// to hold the output until that output diverges from s.
+type lazybuf struct {
+	s   string
+	buf []byte
+	w   int
+}
+
+func (b *lazybuf) index(i int) byte {
+	if b.buf != nil {
+		return b.buf[i]
+	}
+	return b.s[i]
+}
+
+func (b *lazybuf) append(c byte) {
+	if b.buf == nil {
+		if b.w < len(b.s) && b.s[b.w] == c {
+			b.w++
+			return
+		}
+		b.buf = make([]byte, len(b.s))
+		copy(b.buf, b.s[:b.w])
+	}
+	b.buf[b.w] = c
+	b.w++
+}
+
+func (b *lazybuf) string() string {
+	if b.buf == nil {
+		return b.s[:b.w]
+	}
+	return string(b.buf[:b.w])
+}
+
+// Clean returns the shortest path name equivalent to path
+// by purely lexical processing.  It applies the following rules
+// iteratively until no further processing can be done:
+//
+//	1. Replace multiple slashes with a single slash.
+//	2. Eliminate each . path name element (the current directory).
+//	3. Eliminate each inner .. path name element (the parent directory)
+//	   along with the non-.. element that precedes it.
+//	4. Eliminate .. elements that begin a rooted path:
+//	   that is, replace "/.." by "/" at the beginning of a path.
+//
+// The returned path ends in a slash only if it is the root "/".
+//
+// If the result of this process is an empty string, Clean
+// returns the string ".".
+//
+// See also Rob Pike, ``Lexical File Names in Plan 9 or
+// Getting Dot-Dot Right,''
+// http://plan9.bell-labs.com/sys/doc/lexnames.html
+func Clean(path string) string {
+	if path == "" {
+		return "."
+	}
+
+	rooted := path[0] == '/'
+	n := len(path)
+
+	// Invariants:
+	//	reading from path; r is index of next byte to process.
+	//	writing to buf; w is index of next byte to write.
+	//	dotdot is index in buf where .. must stop, either because
+	//		it is the leading slash or it is a leading ../../.. prefix.
+	out := lazybuf{s: path}
+	r, dotdot := 0, 0
+	if rooted {
+		out.append('/')
+		r, dotdot = 1, 1
+	}
+
+	for r < n {
+		switch {
+		case path[r] == '/':
+			// empty path element
+			r++
+		case path[r] == '.' && (r+1 == n || path[r+1] == '/'):
+			// . element
+			r++
+		case path[r] == '.' && path[r+1] == '.' && (r+2 == n || path[r+2] == '/'):
+			// .. element: remove to last /
+			r += 2
+			switch {
+			case out.w > dotdot:
+				// can backtrack
+				out.w--
+				for out.w > dotdot && out.index(out.w) != '/' {
+					out.w--
+				}
+			case !rooted:
+				// cannot backtrack, but not rooted, so append .. element.
+				if out.w > 0 {
+					out.append('/')
+				}
+				out.append('.')
+				out.append('.')
+				dotdot = out.w
+			}
+		default:
+			// real path element.
+			// add slash if needed
+			if rooted && out.w != 1 || !rooted && out.w != 0 {
+				out.append('/')
+			}
+			// copy element
+			for ; r < n && path[r] != '/'; r++ {
+				out.append(path[r])
+			}
+		}
+	}
+
+	// Turn empty string into "."
+	if out.w == 0 {
+		return "."
+	}
+
+	return out.string()
+}
+
+// Split splits path immediately following the final slash.
+// separating it into a directory and file name component.
+// If there is no slash path, Split returns an empty dir and
+// file set to path.
+// The returned values have the property that path = dir+file.
+func Split(path string) (dir, file string) {
+	i := strings.LastIndex(path, "/")
+	return path[:i+1], path[i+1:]
+}
+
+// Join joins any number of path elements into a single path, adding a
+// separating slash if necessary. The result is Cleaned; in particular,
+// all empty strings are ignored.
+func Join(elem ...string) string {
+	for i, e := range elem {
+		if e != "" {
+			return Clean(strings.Join(elem[i:], "/"))
+		}
+	}
+	return ""
+}
+
+// Ext returns the file name extension used by path.
+// The extension is the suffix beginning at the final dot
+// in the final slash-separated element of path;
+// it is empty if there is no dot.
+func Ext(path string) string {
+	for i := len(path) - 1; i >= 0 && path[i] != '/'; i-- {
+		if path[i] == '.' {
+			return path[i:]
+		}
+	}
+	return ""
+}
+
+// Base returns the last element of path.
+// Trailing slashes are removed before extracting the last element.
+// If the path is empty, Base returns ".".
+// If the path consists entirely of slashes, Base returns "/".
+func Base(path string) string {
+	if path == "" {
+		return "."
+	}
+	// Strip trailing slashes.
+	for len(path) > 0 && path[len(path)-1] == '/' {
+		path = path[0 : len(path)-1]
+	}
+	// Find the last element
+	if i := strings.LastIndex(path, "/"); i >= 0 {
+		path = path[i+1:]
+	}
+	// If empty now, it had only slashes.
+	if path == "" {
+		return "/"
+	}
+	return path
+}
+
+// IsAbs returns true if the path is absolute.
+func IsAbs(path string) bool {
+	return len(path) > 0 && path[0] == '/'
+}
+
+// Dir returns all but the last element of path, typically the path's directory.
+// After dropping the final element using Split, the path is Cleaned and trailing
+// slashes are removed.
+// If the path is empty, Dir returns ".".
+// If the path consists entirely of slashes followed by non-slash bytes, Dir
+// returns a single slash. In any other case, the returned path does not end in a
+// slash.
+func Dir(path string) string {
+	dir, _ := Split(path)
+	return Clean(dir)
+}
diff --git a/src/path/path_test.go b/src/path/path_test.go
new file mode 100644
index 000000000..13b585223
--- /dev/null
+++ b/src/path/path_test.go
@@ -0,0 +1,241 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package path
+
+import (
+	"runtime"
+	"testing"
+)
+
+type PathTest struct {
+	path, result string
+}
+
+var cleantests = []PathTest{
+	// Already clean
+	{"", "."},
+	{"abc", "abc"},
+	{"abc/def", "abc/def"},
+	{"a/b/c", "a/b/c"},
+	{".", "."},
+	{"..", ".."},
+	{"../..", "../.."},
+	{"../../abc", "../../abc"},
+	{"/abc", "/abc"},
+	{"/", "/"},
+
+	// Remove trailing slash
+	{"abc/", "abc"},
+	{"abc/def/", "abc/def"},
+	{"a/b/c/", "a/b/c"},
+	{"./", "."},
+	{"../", ".."},
+	{"../../", "../.."},
+	{"/abc/", "/abc"},
+
+	// Remove doubled slash
+	{"abc//def//ghi", "abc/def/ghi"},
+	{"//abc", "/abc"},
+	{"///abc", "/abc"},
+	{"//abc//", "/abc"},
+	{"abc//", "abc"},
+
+	// Remove . elements
+	{"abc/./def", "abc/def"},
+	{"/./abc/def", "/abc/def"},
+	{"abc/.", "abc"},
+
+	// Remove .. elements
+	{"abc/def/ghi/../jkl", "abc/def/jkl"},
+	{"abc/def/../ghi/../jkl", "abc/jkl"},
+	{"abc/def/..", "abc"},
+	{"abc/def/../..", "."},
+	{"/abc/def/../..", "/"},
+	{"abc/def/../../..", ".."},
+	{"/abc/def/../../..", "/"},
+	{"abc/def/../../../ghi/jkl/../../../mno", "../../mno"},
+
+	// Combinations
+	{"abc/./../def", "def"},
+	{"abc//./../def", "def"},
+	{"abc/../../././../def", "../../def"},
+}
+
+func TestClean(t *testing.T) {
+	for _, test := range cleantests {
+		if s := Clean(test.path); s != test.result {
+			t.Errorf("Clean(%q) = %q, want %q", test.path, s, test.result)
+		}
+		if s := Clean(test.result); s != test.result {
+			t.Errorf("Clean(%q) = %q, want %q", test.result, s, test.result)
+		}
+	}
+}
+
+func TestCleanMallocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Log("skipping AllocsPerRun checks; GOMAXPROCS>1")
+		return
+	}
+
+	for _, test := range cleantests {
+		allocs := testing.AllocsPerRun(100, func() { Clean(test.result) })
+		if allocs > 0 {
+			t.Errorf("Clean(%q): %v allocs, want zero", test.result, allocs)
+		}
+	}
+}
+
+type SplitTest struct {
+	path, dir, file string
+}
+
+var splittests = []SplitTest{
+	{"a/b", "a/", "b"},
+	{"a/b/", "a/b/", ""},
+	{"a/", "a/", ""},
+	{"a", "", "a"},
+	{"/", "/", ""},
+}
+
+func TestSplit(t *testing.T) {
+	for _, test := range splittests {
+		if d, f := Split(test.path); d != test.dir || f != test.file {
+			t.Errorf("Split(%q) = %q, %q, want %q, %q", test.path, d, f, test.dir, test.file)
+		}
+	}
+}
+
+type JoinTest struct {
+	elem []string
+	path string
+}
+
+var jointests = []JoinTest{
+	// zero parameters
+	{[]string{}, ""},
+
+	// one parameter
+	{[]string{""}, ""},
+	{[]string{"a"}, "a"},
+
+	// two parameters
+	{[]string{"a", "b"}, "a/b"},
+	{[]string{"a", ""}, "a"},
+	{[]string{"", "b"}, "b"},
+	{[]string{"/", "a"}, "/a"},
+	{[]string{"/", ""}, "/"},
+	{[]string{"a/", "b"}, "a/b"},
+	{[]string{"a/", ""}, "a"},
+	{[]string{"", ""}, ""},
+}
+
+// join takes a []string and passes it to Join.
+func join(elem []string, args ...string) string {
+	args = elem
+	return Join(args...)
+}
+
+func TestJoin(t *testing.T) {
+	for _, test := range jointests {
+		if p := join(test.elem); p != test.path {
+			t.Errorf("join(%q) = %q, want %q", test.elem, p, test.path)
+		}
+	}
+}
+
+type ExtTest struct {
+	path, ext string
+}
+
+var exttests = []ExtTest{
+	{"path.go", ".go"},
+	{"path.pb.go", ".go"},
+	{"a.dir/b", ""},
+	{"a.dir/b.go", ".go"},
+	{"a.dir/", ""},
+}
+
+func TestExt(t *testing.T) {
+	for _, test := range exttests {
+		if x := Ext(test.path); x != test.ext {
+			t.Errorf("Ext(%q) = %q, want %q", test.path, x, test.ext)
+		}
+	}
+}
+
+var basetests = []PathTest{
+	// Already clean
+	{"", "."},
+	{".", "."},
+	{"/.", "."},
+	{"/", "/"},
+	{"////", "/"},
+	{"x/", "x"},
+	{"abc", "abc"},
+	{"abc/def", "def"},
+	{"a/b/.x", ".x"},
+	{"a/b/c.", "c."},
+	{"a/b/c.x", "c.x"},
+}
+
+func TestBase(t *testing.T) {
+	for _, test := range basetests {
+		if s := Base(test.path); s != test.result {
+			t.Errorf("Base(%q) = %q, want %q", test.path, s, test.result)
+		}
+	}
+}
+
+var dirtests = []PathTest{
+	{"", "."},
+	{".", "."},
+	{"/.", "/"},
+	{"/", "/"},
+	{"////", "/"},
+	{"/foo", "/"},
+	{"x/", "x"},
+	{"abc", "."},
+	{"abc/def", "abc"},
+	{"abc////def", "abc"},
+	{"a/b/.x", "a/b"},
+	{"a/b/c.", "a/b"},
+	{"a/b/c.x", "a/b"},
+}
+
+func TestDir(t *testing.T) {
+	for _, test := range dirtests {
+		if s := Dir(test.path); s != test.result {
+			t.Errorf("Dir(%q) = %q, want %q", test.path, s, test.result)
+		}
+	}
+}
+
+type IsAbsTest struct {
+	path  string
+	isAbs bool
+}
+
+var isAbsTests = []IsAbsTest{
+	{"", false},
+	{"/", true},
+	{"/usr/bin/gcc", true},
+	{"..", false},
+	{"/a/../bb", true},
+	{".", false},
+	{"./", false},
+	{"lala", false},
+}
+
+func TestIsAbs(t *testing.T) {
+	for _, test := range isAbsTests {
+		if r := IsAbs(test.path); r != test.isAbs {
+			t.Errorf("IsAbs(%q) = %v, want %v", test.path, r, test.isAbs)
+		}
+	}
+}