21 files changed, 5227 insertions, 0 deletions

diff --git a/src/path/example_test.go b/src/path/example_test.go
new file mode 100644
index 0000000..e30ebd1
--- /dev/null
+++ b/src/path/example_test.go
@@ -0,0 +1,121 @@
+// 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"))
+	fmt.Println(path.Base("/"))
+	fmt.Println(path.Base(""))
+	// 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"
+	// Clean("") = "."
+}
+
+func ExampleDir() {
+	fmt.Println(path.Dir("/a/b/c"))
+	fmt.Println(path.Dir("a/b/c"))
+	fmt.Println(path.Dir("/a/"))
+	fmt.Println(path.Dir("a/"))
+	fmt.Println(path.Dir("/"))
+	fmt.Println(path.Dir(""))
+	// Output:
+	// /a/b
+	// a/b
+	// /a
+	// a
+	// /
+	// .
+}
+
+func ExampleExt() {
+	fmt.Println(path.Ext("/a/b/c/bar.css"))
+	fmt.Println(path.Ext("/"))
+	fmt.Println(path.Ext(""))
+	// Output:
+	// .css
+	//
+	//
+}
+
+func ExampleIsAbs() {
+	fmt.Println(path.IsAbs("/dev/null"))
+	// Output: true
+}
+
+func ExampleJoin() {
+	fmt.Println(path.Join("a", "b", "c"))
+	fmt.Println(path.Join("a", "b/c"))
+	fmt.Println(path.Join("a/b", "c"))
+
+	fmt.Println(path.Join("a/b", "../../../xyz"))
+
+	fmt.Println(path.Join("", ""))
+	fmt.Println(path.Join("a", ""))
+	fmt.Println(path.Join("", "a"))
+
+	// Output:
+	// a/b/c
+	// a/b/c
+	// a/b/c
+	// ../xyz
+	//
+	// a
+	// a
+}
+
+func ExampleMatch() {
+	fmt.Println(path.Match("abc", "abc"))
+	fmt.Println(path.Match("a*", "abc"))
+	fmt.Println(path.Match("a*/b", "a/c/b"))
+	// Output:
+	// true <nil>
+	// true <nil>
+	// false <nil>
+}
+
+func ExampleSplit() {
+	split := func(s string) {
+		dir, file := path.Split(s)
+		fmt.Printf("path.Split(%q) = dir: %q, file: %q\n", s, dir, file)
+	}
+	split("static/myfile.css")
+	split("myfile.css")
+	split("")
+	// Output:
+	// path.Split("static/myfile.css") = dir: "static/", file: "myfile.css"
+	// path.Split("myfile.css") = dir: "", file: "myfile.css"
+	// path.Split("") = dir: "", file: ""
+}
diff --git a/src/path/filepath/example_test.go b/src/path/filepath/example_test.go
new file mode 100644
index 0000000..a1d680e
--- /dev/null
+++ b/src/path/filepath/example_test.go
@@ -0,0 +1,20 @@
+// Copyright 2017 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 (
+	"fmt"
+	"path/filepath"
+)
+
+func ExampleExt() {
+	fmt.Printf("No dots: %q\n", filepath.Ext("index"))
+	fmt.Printf("One dot: %q\n", filepath.Ext("index.js"))
+	fmt.Printf("Two dots: %q\n", filepath.Ext("main.test.js"))
+	// Output:
+	// No dots: ""
+	// One dot: ".js"
+	// Two dots: ".js"
+}
diff --git a/src/path/filepath/example_unix_test.go b/src/path/filepath/example_unix_test.go
new file mode 100644
index 0000000..c9d6944
--- /dev/null
+++ b/src/path/filepath/example_unix_test.go
@@ -0,0 +1,171 @@
+// 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
+}
+
+func ExampleSplit() {
+	paths := []string{
+		"/home/arnie/amelia.jpg",
+		"/mnt/photos/",
+		"rabbit.jpg",
+		"/usr/local//go",
+	}
+	fmt.Println("On Unix:")
+	for _, p := range paths {
+		dir, file := filepath.Split(p)
+		fmt.Printf("input: %q\n\tdir: %q\n\tfile: %q\n", p, dir, file)
+	}
+	// Output:
+	// On Unix:
+	// input: "/home/arnie/amelia.jpg"
+	// 	dir: "/home/arnie/"
+	// 	file: "amelia.jpg"
+	// input: "/mnt/photos/"
+	// 	dir: "/mnt/photos/"
+	// 	file: ""
+	// input: "rabbit.jpg"
+	// 	dir: ""
+	// 	file: "rabbit.jpg"
+	// input: "/usr/local//go"
+	// 	dir: "/usr/local//"
+	// 	file: "go"
+}
+
+func ExampleJoin() {
+	fmt.Println("On Unix:")
+	fmt.Println(filepath.Join("a", "b", "c"))
+	fmt.Println(filepath.Join("a", "b/c"))
+	fmt.Println(filepath.Join("a/b", "c"))
+	fmt.Println(filepath.Join("a/b", "/c"))
+
+	fmt.Println(filepath.Join("a/b", "../../../xyz"))
+
+	// Output:
+	// On Unix:
+	// a/b/c
+	// a/b/c
+	// a/b/c
+	// a/b/c
+	// ../xyz
+}
+
+func ExampleMatch() {
+	fmt.Println("On Unix:")
+	fmt.Println(filepath.Match("/home/catch/*", "/home/catch/foo"))
+	fmt.Println(filepath.Match("/home/catch/*", "/home/catch/foo/bar"))
+	fmt.Println(filepath.Match("/home/?opher", "/home/gopher"))
+	fmt.Println(filepath.Match("/home/\\*", "/home/*"))
+
+	// Output:
+	// On Unix:
+	// true <nil>
+	// false <nil>
+	// true <nil>
+	// true <nil>
+}
+
+func ExampleBase() {
+	fmt.Println("On Unix:")
+	fmt.Println(filepath.Base("/foo/bar/baz.js"))
+	fmt.Println(filepath.Base("/foo/bar/baz"))
+	fmt.Println(filepath.Base("/foo/bar/baz/"))
+	fmt.Println(filepath.Base("dev.txt"))
+	fmt.Println(filepath.Base("../todo.txt"))
+	fmt.Println(filepath.Base(".."))
+	fmt.Println(filepath.Base("."))
+	fmt.Println(filepath.Base("/"))
+	fmt.Println(filepath.Base(""))
+
+	// Output:
+	// On Unix:
+	// baz.js
+	// baz
+	// baz
+	// dev.txt
+	// todo.txt
+	// ..
+	// .
+	// /
+	// .
+}
+
+func ExampleDir() {
+	fmt.Println("On Unix:")
+	fmt.Println(filepath.Dir("/foo/bar/baz.js"))
+	fmt.Println(filepath.Dir("/foo/bar/baz"))
+	fmt.Println(filepath.Dir("/foo/bar/baz/"))
+	fmt.Println(filepath.Dir("/dirty//path///"))
+	fmt.Println(filepath.Dir("dev.txt"))
+	fmt.Println(filepath.Dir("../todo.txt"))
+	fmt.Println(filepath.Dir(".."))
+	fmt.Println(filepath.Dir("."))
+	fmt.Println(filepath.Dir("/"))
+	fmt.Println(filepath.Dir(""))
+
+	// Output:
+	// On Unix:
+	// /foo/bar
+	// /foo/bar
+	// /foo/bar/baz
+	// /dirty/path
+	// .
+	// ..
+	// .
+	// .
+	// /
+	// .
+}
+
+func ExampleIsAbs() {
+	fmt.Println("On Unix:")
+	fmt.Println(filepath.IsAbs("/home/gopher"))
+	fmt.Println(filepath.IsAbs(".bashrc"))
+	fmt.Println(filepath.IsAbs(".."))
+	fmt.Println(filepath.IsAbs("."))
+	fmt.Println(filepath.IsAbs("/"))
+	fmt.Println(filepath.IsAbs(""))
+
+	// Output:
+	// On Unix:
+	// true
+	// false
+	// false
+	// false
+	// true
+	// false
+}
diff --git a/src/path/filepath/example_unix_walk_test.go b/src/path/filepath/example_unix_walk_test.go
new file mode 100644
index 0000000..c8a818f
--- /dev/null
+++ b/src/path/filepath/example_unix_walk_test.go
@@ -0,0 +1,66 @@
+// Copyright 2018 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"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+func prepareTestDirTree(tree string) (string, error) {
+	tmpDir, err := os.MkdirTemp("", "")
+	if err != nil {
+		return "", fmt.Errorf("error creating temp directory: %v\n", err)
+	}
+
+	err = os.MkdirAll(filepath.Join(tmpDir, tree), 0755)
+	if err != nil {
+		os.RemoveAll(tmpDir)
+		return "", err
+	}
+
+	return tmpDir, nil
+}
+
+func ExampleWalk() {
+	tmpDir, err := prepareTestDirTree("dir/to/walk/skip")
+	if err != nil {
+		fmt.Printf("unable to create test dir tree: %v\n", err)
+		return
+	}
+	defer os.RemoveAll(tmpDir)
+	os.Chdir(tmpDir)
+
+	subDirToSkip := "skip"
+
+	fmt.Println("On Unix:")
+	err = filepath.Walk(".", func(path string, info fs.FileInfo, err error) error {
+		if err != nil {
+			fmt.Printf("prevent panic by handling failure accessing a path %q: %v\n", path, err)
+			return err
+		}
+		if info.IsDir() && info.Name() == subDirToSkip {
+			fmt.Printf("skipping a dir without errors: %+v \n", info.Name())
+			return filepath.SkipDir
+		}
+		fmt.Printf("visited file or dir: %q\n", path)
+		return nil
+	})
+	if err != nil {
+		fmt.Printf("error walking the path %q: %v\n", tmpDir, err)
+		return
+	}
+	// Output:
+	// On Unix:
+	// visited file or dir: "."
+	// visited file or dir: "dir"
+	// visited file or dir: "dir/to"
+	// visited file or dir: "dir/to/walk"
+	// skipping a dir without errors: skip
+}
diff --git a/src/path/filepath/export_test.go b/src/path/filepath/export_test.go
new file mode 100644
index 0000000..0cf9e3b
--- /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/export_windows_test.go b/src/path/filepath/export_windows_test.go
new file mode 100644
index 0000000..a7e2e64
--- /dev/null
+++ b/src/path/filepath/export_windows_test.go
@@ -0,0 +1,10 @@
+// Copyright 2016 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 (
+	ToNorm   = toNorm
+	NormBase = normBase
+)
diff --git a/src/path/filepath/match.go b/src/path/filepath/match.go
new file mode 100644
index 0000000..c77a269
--- /dev/null
+++ b/src/path/filepath/match.go
@@ -0,0 +1,360 @@
+// 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 pattern was malformed.
+var ErrBadPattern = errors.New("syntax error in pattern")
+
+// Match reports whether 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.Contains(name, string(Separator)), 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) {
+	// failed records whether the match has failed.
+	// After the match fails, the loop continues on processing chunk,
+	// checking that the pattern is well-formed but no longer reading s.
+	failed := false
+	for len(chunk) > 0 {
+		if !failed && len(s) == 0 {
+			failed = true
+		}
+		switch chunk[0] {
+		case '[':
+			// character class
+			var r rune
+			if !failed {
+				var n int
+				r, n = utf8.DecodeRuneInString(s)
+				s = s[n:]
+			}
+			chunk = chunk[1:]
+			// possibly negated
+			negated := false
+			if len(chunk) > 0 && chunk[0] == '^' {
+				negated = true
+				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 "", false, err
+				}
+				hi = lo
+				if chunk[0] == '-' {
+					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
+						return "", false, err
+					}
+				}
+				if lo <= r && r <= hi {
+					match = true
+				}
+				nrange++
+			}
+			if match == negated {
+				failed = true
+			}
+
+		case '?':
+			if !failed {
+				if s[0] == Separator {
+					failed = true
+				}
+				_, n := utf8.DecodeRuneInString(s)
+				s = s[n:]
+			}
+			chunk = chunk[1:]
+
+		case '\\':
+			if runtime.GOOS != "windows" {
+				chunk = chunk[1:]
+				if len(chunk) == 0 {
+					return "", false, ErrBadPattern
+				}
+			}
+			fallthrough
+
+		default:
+			if !failed {
+				if chunk[0] != s[0] {
+					failed = true
+				}
+				s = s[1:]
+			}
+			chunk = chunk[1:]
+		}
+	}
+	if failed {
+		return "", false, nil
+	}
+	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 '/').
+//
+// Glob ignores file system errors such as I/O errors reading directories.
+// The only possible returned error is ErrBadPattern, when pattern
+// is malformed.
+func Glob(pattern string) (matches []string, err error) {
+	// Check pattern is well-formed.
+	if _, err := Match(pattern, ""); err != nil {
+		return nil, err
+	}
+	if !hasMeta(pattern) {
+		if _, err = os.Lstat(pattern); err != nil {
+			return nil, nil
+		}
+		return []string{pattern}, nil
+	}
+
+	dir, file := Split(pattern)
+	volumeLen := 0
+	if runtime.GOOS == "windows" {
+		volumeLen, dir = cleanGlobPathWindows(dir)
+	} else {
+		dir = cleanGlobPath(dir)
+	}
+
+	if !hasMeta(dir[volumeLen:]) {
+		return glob(dir, file, nil)
+	}
+
+	// Prevent infinite recursion. See issue 15879.
+	if dir == pattern {
+		return nil, ErrBadPattern
+	}
+
+	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
+}
+
+// cleanGlobPath prepares path for glob matching.
+func cleanGlobPath(path string) string {
+	switch path {
+	case "":
+		return "."
+	case string(Separator):
+		// do nothing to the path
+		return path
+	default:
+		return path[0 : len(path)-1] // chop off trailing separator
+	}
+}
+
+// cleanGlobPathWindows is windows version of cleanGlobPath.
+func cleanGlobPathWindows(path string) (prefixLen int, cleaned string) {
+	vollen := volumeNameLen(path)
+	switch {
+	case path == "":
+		return 0, "."
+	case vollen+1 == len(path) && os.IsPathSeparator(path[len(path)-1]): // /, \, C:\ and C:/
+		// do nothing to the path
+		return vollen + 1, path
+	case vollen == len(path) && len(path) == 2: // C:
+		return vollen, path + "." // convert C: into C:.
+	default:
+		if vollen >= len(path) {
+			vollen = len(path) - 1
+		}
+		return vollen, path[0 : len(path)-1] // chop off trailing separator
+	}
+}
+
+// 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 // ignore I/O error
+	}
+	if !fi.IsDir() {
+		return // ignore I/O error
+	}
+	d, err := os.Open(dir)
+	if err != nil {
+		return // ignore I/O error
+	}
+	defer d.Close()
+
+	names, _ := d.Readdirnames(-1)
+	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 reports whether path contains any of the magic characters
+// recognized by Match.
+func hasMeta(path string) bool {
+	magicChars := `*?[`
+	if runtime.GOOS != "windows" {
+		magicChars = `*?[\`
+	}
+	return strings.ContainsAny(path, magicChars)
+}
diff --git a/src/path/filepath/match_test.go b/src/path/filepath/match_test.go
new file mode 100644
index 0000000..48880ea
--- /dev/null
+++ b/src/path/filepath/match_test.go
@@ -0,0 +1,392 @@
+// 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 (
+	"fmt"
+	"internal/testenv"
+	"os"
+	. "path/filepath"
+	"reflect"
+	"runtime"
+	"sort"
+	"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, ErrBadPattern},
+	{"a[", "ab", false, ErrBadPattern},
+	{"a[", "x", false, ErrBadPattern},
+	{"a/b[", "x", 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.Contains(pattern, "\\") {
+				// 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 reports whether 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) {
+	bad := []string{`[]`, `nonexist/[]`}
+	for _, pattern := range bad {
+		if _, err := Glob(pattern); err != ErrBadPattern {
+			t.Errorf("Glob(%#q) returned err=%v, want ErrBadPattern", pattern, err)
+		}
+	}
+}
+
+func TestGlobUNC(t *testing.T) {
+	// Just make sure this runs without crashing for now.
+	// See issue 15879.
+	Glob(`\\?\C:\*`)
+}
+
+var globSymlinkTests = []struct {
+	path, dest string
+	brokenLink bool
+}{
+	{"test1", "link1", false},
+	{"test2", "link2", true},
+}
+
+func TestGlobSymlink(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir, err := os.MkdirTemp("", "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)
+		}
+	}
+}
+
+type globTest struct {
+	pattern string
+	matches []string
+}
+
+func (test *globTest) buildWant(root string) []string {
+	want := make([]string, 0)
+	for _, m := range test.matches {
+		want = append(want, root+FromSlash(m))
+	}
+	sort.Strings(want)
+	return want
+}
+
+func (test *globTest) globAbs(root, rootPattern string) error {
+	p := FromSlash(rootPattern + `\` + test.pattern)
+	have, err := Glob(p)
+	if err != nil {
+		return err
+	}
+	sort.Strings(have)
+	want := test.buildWant(root + `\`)
+	if strings.Join(want, "_") == strings.Join(have, "_") {
+		return nil
+	}
+	return fmt.Errorf("Glob(%q) returns %q, but %q expected", p, have, want)
+}
+
+func (test *globTest) globRel(root string) error {
+	p := root + FromSlash(test.pattern)
+	have, err := Glob(p)
+	if err != nil {
+		return err
+	}
+	sort.Strings(have)
+	want := test.buildWant(root)
+	if strings.Join(want, "_") == strings.Join(have, "_") {
+		return nil
+	}
+	// try also matching version without root prefix
+	wantWithNoRoot := test.buildWant("")
+	if strings.Join(wantWithNoRoot, "_") == strings.Join(have, "_") {
+		return nil
+	}
+	return fmt.Errorf("Glob(%q) returns %q, but %q expected", p, have, want)
+}
+
+func TestWindowsGlob(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skipf("skipping windows specific test")
+	}
+
+	tmpDir, err := os.MkdirTemp("", "TestWindowsGlob")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// /tmp may itself be a symlink
+	tmpDir, err = EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal("eval symlink for tmp dir:", err)
+	}
+
+	if len(tmpDir) < 3 {
+		t.Fatalf("tmpDir path %q is too short", tmpDir)
+	}
+	if tmpDir[1] != ':' {
+		t.Fatalf("tmpDir path %q must have drive letter in it", tmpDir)
+	}
+
+	dirs := []string{
+		"a",
+		"b",
+		"dir/d/bin",
+	}
+	files := []string{
+		"dir/d/bin/git.exe",
+	}
+	for _, dir := range dirs {
+		err := os.MkdirAll(Join(tmpDir, dir), 0777)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, file := range files {
+		err := os.WriteFile(Join(tmpDir, file), nil, 0666)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	tests := []globTest{
+		{"a", []string{"a"}},
+		{"b", []string{"b"}},
+		{"c", []string{}},
+		{"*", []string{"a", "b", "dir"}},
+		{"d*", []string{"dir"}},
+		{"*i*", []string{"dir"}},
+		{"*r", []string{"dir"}},
+		{"?ir", []string{"dir"}},
+		{"?r", []string{}},
+		{"d*/*/bin/git.exe", []string{"dir/d/bin/git.exe"}},
+	}
+
+	// test absolute paths
+	for _, test := range tests {
+		var p string
+		err = test.globAbs(tmpDir, tmpDir)
+		if err != nil {
+			t.Error(err)
+		}
+		// test C:\*Documents and Settings\...
+		p = tmpDir
+		p = strings.Replace(p, `:\`, `:\*`, 1)
+		err = test.globAbs(tmpDir, p)
+		if err != nil {
+			t.Error(err)
+		}
+		// test C:\Documents and Settings*\...
+		p = tmpDir
+		p = strings.Replace(p, `:\`, `:`, 1)
+		p = strings.Replace(p, `\`, `*\`, 1)
+		p = strings.Replace(p, `:`, `:\`, 1)
+		err = test.globAbs(tmpDir, p)
+		if err != nil {
+			t.Error(err)
+		}
+	}
+
+	// test relative paths
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.Chdir(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := os.Chdir(wd)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+	for _, test := range tests {
+		err := test.globRel("")
+		if err != nil {
+			t.Error(err)
+		}
+		err = test.globRel(`.\`)
+		if err != nil {
+			t.Error(err)
+		}
+		err = test.globRel(tmpDir[:2]) // C:
+		if err != nil {
+			t.Error(err)
+		}
+	}
+}
+
+func TestNonWindowsGlobEscape(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skipf("skipping non-windows specific test")
+	}
+	pattern := `\match.go`
+	want := []string{"match.go"}
+	matches, err := Glob(pattern)
+	if err != nil {
+		t.Fatalf("Glob error for %q: %s", pattern, err)
+	}
+	if !reflect.DeepEqual(matches, want) {
+		t.Fatalf("Glob(%#q) = %v want %v", pattern, matches, want)
+	}
+}
diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go
new file mode 100644
index 0000000..2e7b439
--- /dev/null
+++ b/src/path/filepath/path.go
@@ -0,0 +1,596 @@
+// 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.
+//
+// The filepath package uses either forward slashes or backslashes,
+// depending on the operating system. To process paths such as URLs
+// that always use forward slashes regardless of the operating
+// system, see the path package.
+package filepath
+
+import (
+	"errors"
+	"io/fs"
+	"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.
+//
+// Finally, any occurrences of slash are replaced by Separator.
+//
+// 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,''
+// https://9p.io/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.ReplaceAll(path, string(Separator), "/")
+}
+
+// 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.ReplaceAll(path, "/", string(Separator))
+}
+
+// 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,
+// separating them with an OS specific Separator. Empty elements
+// are ignored. The result is Cleaned. However, if the argument
+// list is empty or all its elements are empty, Join returns
+// an empty string.
+// On Windows, the result will only be a UNC path if the first
+// non-empty element is a UNC path.
+func Join(elem ...string) string {
+	return join(elem)
+}
+
+// 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.
+// EvalSymlinks calls Clean on the result.
+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.
+// Abs calls Clean on the result.
+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.
+// Rel calls Clean on the result.
+func Rel(basepath, targpath string) (string, error) {
+	baseVol := VolumeName(basepath)
+	targVol := VolumeName(targpath)
+	base := Clean(basepath)
+	targ := Clean(targpath)
+	if sameWord(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 || !sameWord(baseVol, targVol) {
+		return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
+	}
+	// 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 !sameWord(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 " + targpath + " relative to " + basepath)
+	}
+	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 error = fs.SkipDir
+
+// WalkFunc is the type of the function called by Walk to visit each each
+// file or directory.
+//
+// The path argument contains the argument to Walk as a prefix.
+// That is, if Walk is called with root argument "dir" and finds a file
+// named "a" in that directory, the walk function will be called with
+// argument "dir/a".
+//
+// The directory and file are joined with Join, which may clean the
+// directory name: if Walk is called with the root argument "x/../dir"
+// and finds a file named "a" in that directory, the walk function will
+// be called with argument "dir/a", not "x/../dir/a".
+//
+// The info argument is the fs.FileInfo for the named path.
+//
+// The error result returned by the function controls how Walk continues.
+// If the function returns the special value SkipDir, Walk skips the
+// current directory (path if info.IsDir() is true, otherwise path's
+// parent directory). Otherwise, if the function returns a non-nil error,
+// Walk stops entirely and returns that error.
+//
+// The err argument reports an error related to path, signaling that Walk
+// will not walk into that directory. The function can decide how to
+// handle that error; as described earlier, returning the error will
+// cause Walk to stop walking the entire tree.
+//
+// Walk calls the function with a non-nil err argument in two cases.
+//
+// First, if an os.Lstat on the root directory or any directory or file
+// in the tree fails, Walk calls the function with path set to that
+// directory or file's path, info set to nil, and err set to the error
+// from os.Lstat.
+//
+// Second, if a directory's Readdirnames method fails, Walk calls the
+// function with path set to the directory's path, info, set to an
+// fs.FileInfo describing the directory, and err set to the error from
+// Readdirnames.
+type WalkFunc func(path string, info fs.FileInfo, err error) error
+
+var lstat = os.Lstat // for testing
+
+// walkDir recursively descends path, calling walkDirFn.
+func walkDir(path string, d fs.DirEntry, walkDirFn fs.WalkDirFunc) error {
+	if err := walkDirFn(path, d, nil); err != nil || !d.IsDir() {
+		if err == SkipDir && d.IsDir() {
+			// Successfully skipped directory.
+			err = nil
+		}
+		return err
+	}
+
+	dirs, err := readDir(path)
+	if err != nil {
+		// Second call, to report ReadDir error.
+		err = walkDirFn(path, d, err)
+		if err != nil {
+			return err
+		}
+	}
+
+	for _, d1 := range dirs {
+		path1 := Join(path, d1.Name())
+		if err := walkDir(path1, d1, walkDirFn); err != nil {
+			if err == SkipDir {
+				break
+			}
+			return err
+		}
+	}
+	return nil
+}
+
+// walk recursively descends path, calling walkFn.
+func walk(path string, info fs.FileInfo, walkFn WalkFunc) error {
+	if !info.IsDir() {
+		return walkFn(path, info, nil)
+	}
+
+	names, err := readDirNames(path)
+	err1 := walkFn(path, info, err)
+	// If err != nil, walk can't walk into this directory.
+	// err1 != nil means walkFn want walk to skip this directory or stop walking.
+	// Therefore, if one of err and err1 isn't nil, walk will return.
+	if err != nil || err1 != nil {
+		// The caller's behavior is controlled by the return value, which is decided
+		// by walkFn. walkFn may ignore err and return nil.
+		// If walkFn returns SkipDir, it will be handled by the caller.
+		// So walk should return whatever walkFn returns.
+		return err1
+	}
+
+	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
+}
+
+// WalkDir walks the file tree rooted at root, calling fn for each file or
+// directory in the tree, including root.
+//
+// All errors that arise visiting files and directories are filtered by fn:
+// see the fs.WalkDirFunc documentation for details.
+//
+// The files are walked in lexical order, which makes the output deterministic
+// but requires WalkDir to read an entire directory into memory before proceeding
+// to walk that directory.
+//
+// WalkDir does not follow symbolic links.
+func WalkDir(root string, fn fs.WalkDirFunc) error {
+	info, err := os.Lstat(root)
+	if err != nil {
+		err = fn(root, nil, err)
+	} else {
+		err = walkDir(root, &statDirEntry{info}, fn)
+	}
+	if err == SkipDir {
+		return nil
+	}
+	return err
+}
+
+type statDirEntry struct {
+	info fs.FileInfo
+}
+
+func (d *statDirEntry) Name() string               { return d.info.Name() }
+func (d *statDirEntry) IsDir() bool                { return d.info.IsDir() }
+func (d *statDirEntry) Type() fs.FileMode          { return d.info.Mode().Type() }
+func (d *statDirEntry) Info() (fs.FileInfo, error) { return d.info, nil }
+
+// Walk walks the file tree rooted at root, calling fn for each file or
+// directory in the tree, including root.
+//
+// All errors that arise visiting files and directories are filtered by fn:
+// see the WalkFunc documentation for details.
+//
+// The files are walked in lexical order, which makes the output deterministic
+// but requires Walk to read an entire directory into memory before proceeding
+// to walk that directory.
+//
+// Walk does not follow symbolic links.
+//
+// Walk is less efficient than WalkDir, introduced in Go 1.16,
+// which avoids calling os.Lstat on every visited file or directory.
+func Walk(root string, fn WalkFunc) error {
+	info, err := os.Lstat(root)
+	if err != nil {
+		err = fn(root, nil, err)
+	} else {
+		err = walk(root, info, fn)
+	}
+	if err == SkipDir {
+		return nil
+	}
+	return err
+}
+
+// readDir reads the directory named by dirname and returns
+// a sorted list of directory entries.
+func readDir(dirname string) ([]fs.DirEntry, error) {
+	f, err := os.Open(dirname)
+	if err != nil {
+		return nil, err
+	}
+	dirs, err := f.ReadDir(-1)
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+	sort.Slice(dirs, func(i, j int) bool { return dirs[i].Name() < dirs[j].Name() })
+	return dirs, nil
+}
+
+// readDirNames reads the directory named by dirname and returns
+// a sorted list of directory entry names.
+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, Dir calls Clean on the path 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])
+	if dir == "." && len(vol) > 2 {
+		// must be UNC
+		return vol
+	}
+	return vol + dir
+}
+
+// VolumeName returns leading volume name.
+// Given "C:\foo\bar" it returns "C:" on Windows.
+// Given "\\host\share\foo" it returns "\\host\share".
+// On other platforms it returns "".
+func VolumeName(path string) 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 0000000..ec792fc
--- /dev/null
+++ b/src/path/filepath/path_plan9.go
@@ -0,0 +1,51 @@
+// 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 reports whether 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.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
+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)
+}
+
+func join(elem []string) string {
+	// If there's a bug here, fix the logic in ./path_unix.go too.
+	for i, e := range elem {
+		if e != "" {
+			return Clean(strings.Join(elem[i:], string(Separator)))
+		}
+	}
+	return ""
+}
+
+func sameWord(a, b string) bool {
+	return a == b
+}
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
new file mode 100644
index 0000000..8616256
--- /dev/null
+++ b/src/path/filepath/path_test.go
@@ -0,0 +1,1537 @@
+// 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"
+	"fmt"
+	"internal/testenv"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"sort"
+	"strings"
+	"syscall"
+	"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"},
+	{"/", "/"},
+
+	// 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{"/"}, "/"},
+	{[]string{"a"}, "a"},
+
+	// two parameters
+	{[]string{"a", "b"}, "a/b"},
+	{[]string{"a", ""}, "a"},
+	{[]string{"", "b"}, "b"},
+	{[]string{"/", "a"}, "/a"},
+	{[]string{"/", "a/b"}, "/a/b"},
+	{[]string{"/", ""}, "/"},
+	{[]string{"//", "a"}, "/a"},
+	{[]string{"/a", "b"}, "/a/b"},
+	{[]string{"a/", "b"}, "a/b"},
+	{[]string{"a/", ""}, "a"},
+	{[]string{"", ""}, ""},
+
+	// three parameters
+	{[]string{"/", "a", "b"}, "/a/b"},
+}
+
+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:`, `a`}, `C:a`},
+	{[]string{`C:`, `a\b`}, `C:a\b`},
+	{[]string{`C:`, `a`, `b`}, `C:a\b`},
+	{[]string{`C:`, ``, `b`}, `C:b`},
+	{[]string{`C:`, ``, ``, `b`}, `C:b`},
+	{[]string{`C:`, ``}, `C:.`},
+	{[]string{`C:`, ``, ``}, `C:.`},
+	{[]string{`C:.`, `a`}, `C:a`},
+	{[]string{`C:a`, `b`}, `C:a\b`},
+	{[]string{`C:a`, `b`, `d`}, `C:a\b\d`},
+	{[]string{`\\host\share`, `foo`}, `\\host\share\foo`},
+	{[]string{`\\host\share\foo`}, `\\host\share\foo`},
+	{[]string{`//host/share`, `foo/bar`}, `\\host\share\foo\bar`},
+	{[]string{`\`}, `\`},
+	{[]string{`\`, ``}, `\`},
+	{[]string{`\`, `a`}, `\a`},
+	{[]string{`\\`, `a`}, `\a`},
+	{[]string{`\`, `a`, `b`}, `\a\b`},
+	{[]string{`\\`, `a`, `b`}, `\a\b`},
+	{[]string{`\`, `\\a\b`, `c`}, `\a\b\c`},
+	{[]string{`\\a`, `b`, `c`}, `\a\b\c`},
+	{[]string{`\\a\`, `b`, `c`}, `\a\b\c`},
+}
+
+func TestJoin(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		jointests = append(jointests, winjointests...)
+	}
+	for _, test := range jointests {
+		expected := filepath.FromSlash(test.path)
+		if p := filepath.Join(test.elem...); p != expected {
+			t.Errorf("join(%q) = %q, want %q", test.elem, p, expected)
+		}
+	}
+}
+
+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(d fs.DirEntry, err error, errors *[]error, clear bool) error {
+	name := d.Name()
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.name == name {
+			n.mark++
+		}
+	})
+	if err != nil {
+		*errors = append(*errors, err)
+		if clear {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+func chtmpdir(t *testing.T) (restore func()) {
+	oldwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	d, err := os.MkdirTemp("", "test")
+	if err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	if err := os.Chdir(d); err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	return func() {
+		if err := os.Chdir(oldwd); err != nil {
+			t.Fatalf("chtmpdir: %v", err)
+		}
+		os.RemoveAll(d)
+	}
+}
+
+func TestWalk(t *testing.T) {
+	walk := func(root string, fn fs.WalkDirFunc) error {
+		return filepath.Walk(root, func(path string, info fs.FileInfo, err error) error {
+			return fn(path, &statDirEntry{info}, err)
+		})
+	}
+	testWalk(t, walk, 1)
+}
+
+type statDirEntry struct {
+	info fs.FileInfo
+}
+
+func (d *statDirEntry) Name() string               { return d.info.Name() }
+func (d *statDirEntry) IsDir() bool                { return d.info.IsDir() }
+func (d *statDirEntry) Type() fs.FileMode          { return d.info.Mode().Type() }
+func (d *statDirEntry) Info() (fs.FileInfo, error) { return d.info, nil }
+
+func TestWalkDir(t *testing.T) {
+	testWalk(t, filepath.WalkDir, 2)
+}
+
+func testWalk(t *testing.T, walk func(string, fs.WalkDirFunc) error, errVisit int) {
+	if runtime.GOOS == "ios" {
+		restore := chtmpdir(t)
+		defer restore()
+	}
+
+	tmpDir, err := os.MkdirTemp("", "TestWalk")
+	if err != nil {
+		t.Fatal("creating temp dir:", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	origDir, err := os.Getwd()
+	if err != nil {
+		t.Fatal("finding working dir:", err)
+	}
+	if err = os.Chdir(tmpDir); err != nil {
+		t.Fatal("entering temp dir:", err)
+	}
+	defer os.Chdir(origDir)
+
+	makeTree(t)
+	errors := make([]error, 0, 10)
+	clear := true
+	markFn := func(path string, d fs.DirEntry, err error) error {
+		return mark(d, err, &errors, clear)
+	}
+	// Expect no errors.
+	err = 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]
+
+	t.Run("PermErr", func(t *testing.T) {
+		// 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 runtime.GOOS == "windows" {
+			t.Skip("skipping on Windows")
+		}
+		if os.Getuid() == 0 {
+			t.Skip("skipping as root")
+		}
+		if testing.Short() {
+			t.Skip("skipping in short mode")
+		}
+
+		// 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 -= errVisit
+		tree.entries[3].mark -= errVisit
+		err := 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 -= errVisit
+		tree.entries[3].mark -= errVisit
+		clear = false // error will stop processing
+		err = 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)
+	})
+}
+
+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 TestWalkSkipDirOnFile(t *testing.T) {
+	td, err := os.MkdirTemp("", "walktest")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(td)
+
+	if err := os.MkdirAll(filepath.Join(td, "dir"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	touch(t, filepath.Join(td, "dir/foo1"))
+	touch(t, filepath.Join(td, "dir/foo2"))
+
+	sawFoo2 := false
+	walker := func(path string) error {
+		if strings.HasSuffix(path, "foo2") {
+			sawFoo2 = true
+		}
+		if strings.HasSuffix(path, "foo1") {
+			return filepath.SkipDir
+		}
+		return nil
+	}
+	walkFn := func(path string, _ fs.FileInfo, _ error) error { return walker(path) }
+	walkDirFn := func(path string, _ fs.DirEntry, _ error) error { return walker(path) }
+
+	check := func(t *testing.T, walk func(root string) error, root string) {
+		t.Helper()
+		sawFoo2 = false
+		err = walk(root)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if sawFoo2 {
+			t.Errorf("SkipDir on file foo1 did not block processing of foo2")
+		}
+	}
+
+	t.Run("Walk", func(t *testing.T) {
+		Walk := func(root string) error { return filepath.Walk(td, walkFn) }
+		check(t, Walk, td)
+		check(t, Walk, filepath.Join(td, "dir"))
+	})
+	t.Run("WalkDir", func(t *testing.T) {
+		WalkDir := func(root string) error { return filepath.WalkDir(td, walkDirFn) }
+		check(t, WalkDir, td)
+		check(t, WalkDir, filepath.Join(td, "dir"))
+	})
+}
+
+func TestWalkFileError(t *testing.T) {
+	td, err := os.MkdirTemp("", "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) (fs.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 fs.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\`, `\\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})
+		}
+		// Test reserved names.
+		tests = append(tests, IsAbsTest{os.DevNull, true})
+		tests = append(tests, IsAbsTest{"NUL", true})
+		tests = append(tests, IsAbsTest{"nul", true})
+		tests = append(tests, IsAbsTest{"CON", true})
+	} 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", "/"},
+	{"test/link4", "../test2"},
+	{"test2", "test/dir"},
+	// Issue 23444.
+	{"src", ""},
+	{"src/pool", ""},
+	{"src/pool/test", ""},
+	{"src/versions", ""},
+	{"src/versions/current", "../../version"},
+	{"src/versions/v1", ""},
+	{"src/versions/v1/modules", ""},
+	{"src/versions/v1/modules/test", "../../../pool/test"},
+	{"version", "src/versions/v1"},
+}
+
+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", "/"},
+	{"test/link4/..", "test"},
+	{"src/versions/current/modules/test", "src/pool/test"},
+}
+
+// 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, path, want string) {
+	have, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		t.Errorf("EvalSymlinks(%q) error: %v", path, err)
+		return
+	}
+	if filepath.Clean(have) != filepath.Clean(want) {
+		t.Errorf("EvalSymlinks(%q) returns %q, want %q", path, have, want)
+	}
+}
+
+func testEvalSymlinksAfterChdir(t *testing.T, wd, path, want string) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := os.Chdir(cwd)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	err = os.Chdir(wd)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	have, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		t.Errorf("EvalSymlinks(%q) in %q directory error: %v", path, wd, err)
+		return
+	}
+	if filepath.Clean(have) != filepath.Clean(want) {
+		t.Errorf("EvalSymlinks(%q) in %q directory returns %q, want %q", path, wd, have, want)
+	}
+}
+
+func TestEvalSymlinks(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir, err := os.MkdirTemp("", "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 {
+			err = os.Symlink(d.dest, path)
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Evaluate the symlink farm.
+	for _, test := range EvalSymlinksTests {
+		path := simpleJoin(tmpDir, test.path)
+
+		dest := simpleJoin(tmpDir, test.dest)
+		if filepath.IsAbs(test.dest) || os.IsPathSeparator(test.dest[0]) {
+			dest = test.dest
+		}
+		testEvalSymlinks(t, path, dest)
+
+		// test EvalSymlinks(".")
+		testEvalSymlinksAfterChdir(t, path, ".", ".")
+
+		// test EvalSymlinks("C:.") on Windows
+		if runtime.GOOS == "windows" {
+			volDot := filepath.VolumeName(tmpDir) + "."
+			testEvalSymlinksAfterChdir(t, path, volDot, volDot)
+		}
+
+		// test EvalSymlinks(".."+path)
+		dotdotPath := simpleJoin("..", test.dest)
+		if filepath.IsAbs(test.dest) || os.IsPathSeparator(test.dest[0]) {
+			dotdotPath = test.dest
+		}
+		testEvalSymlinksAfterChdir(t,
+			simpleJoin(tmpDir, "test"),
+			simpleJoin("..", test.path),
+			dotdotPath)
+
+		// test EvalSymlinks(p) where p is relative path
+		testEvalSymlinksAfterChdir(t, tmpDir, test.path, test.dest)
+	}
+}
+
+func TestEvalSymlinksIsNotExist(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	defer chtmpdir(t)()
+
+	_, err := filepath.EvalSymlinks("notexist")
+	if !os.IsNotExist(err) {
+		t.Errorf("expected the file is not found, got %v\n", err)
+	}
+
+	err = os.Symlink("notexist", "link")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove("link")
+
+	_, err = filepath.EvalSymlinks("link")
+	if !os.IsNotExist(err) {
+		t.Errorf("expected the file is not found, got %v\n", err)
+	}
+}
+
+func TestIssue13582(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir, err := os.MkdirTemp("", "issue13582")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	dir := filepath.Join(tmpDir, "dir")
+	err = os.Mkdir(dir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	linkToDir := filepath.Join(tmpDir, "link_to_dir")
+	err = os.Symlink(dir, linkToDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	file := filepath.Join(linkToDir, "file")
+	err = os.WriteFile(file, nil, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	link1 := filepath.Join(linkToDir, "link1")
+	err = os.Symlink(file, link1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	link2 := filepath.Join(linkToDir, "link2")
+	err = os.Symlink(link1, link2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// /tmp may itself be a symlink!
+	realTmpDir, err := filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	realDir := filepath.Join(realTmpDir, "dir")
+	realFile := filepath.Join(realDir, "file")
+
+	tests := []struct {
+		path, want string
+	}{
+		{dir, realDir},
+		{linkToDir, realDir},
+		{file, realFile},
+		{link1, realFile},
+		{link2, realFile},
+	}
+	for i, test := range tests {
+		have, err := filepath.EvalSymlinks(test.path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if have != test.want {
+			t.Errorf("test#%d: EvalSymlinks(%q) returns %q, want %q", i, test.path, have, test.want)
+		}
+	}
+}
+
+// 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",
+	"b/",
+	"../a",
+	"../a/b",
+	"../a/b/./c/../../.././a",
+	"../a/b/./c/../../.././a/",
+	"$",
+	"$/.",
+	"$/a/../a/b",
+	"$/a/b/c/../../.././a",
+	"$/a/b/c/../../.././a/",
+}
+
+func TestAbs(t *testing.T) {
+	root, err := os.MkdirTemp("", "TestAbs")
+	if err != nil {
+		t.Fatal("TempDir failed: ", err)
+	}
+	defer os.RemoveAll(root)
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal("getwd failed: ", err)
+	}
+	err = os.Chdir(root)
+	if err != nil {
+		t.Fatal("chdir failed: ", err)
+	}
+	defer os.Chdir(wd)
+
+	for _, dir := range absTestDirs {
+		err = os.Mkdir(dir, 0777)
+		if err != nil {
+			t.Fatal("Mkdir failed: ", err)
+		}
+	}
+
+	if runtime.GOOS == "windows" {
+		vol := filepath.VolumeName(root)
+		var extra []string
+		for _, path := range absTests {
+			if strings.Contains(path, "$") {
+				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.ReplaceAll(path, "$", root)
+		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(abspath) && abspath != filepath.Clean(abspath) {
+			t.Errorf("Abs(%q)=%q, isn't clean", path, abspath)
+		}
+	}
+}
+
+// Empty path needs to be special-cased on Windows. See golang.org/issue/24441.
+// We test it separately from all other absTests because the empty string is not
+// a valid path, so it can't be used with os.Stat.
+func TestAbsEmptyString(t *testing.T) {
+	root, err := os.MkdirTemp("", "TestAbsEmptyString")
+	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)
+
+	info, err := os.Stat(root)
+	if err != nil {
+		t.Fatalf("%s: %s", root, err)
+	}
+
+	abspath, err := filepath.Abs("")
+	if err != nil {
+		t.Fatalf(`Abs("") error: %v`, err)
+	}
+	absinfo, err := os.Stat(abspath)
+	if err != nil || !os.SameFile(absinfo, info) {
+		t.Errorf(`Abs("")=%q, not the same file`, abspath)
+	}
+	if !filepath.IsAbs(abspath) {
+		t.Errorf(`Abs("")=%q, not an absolute path`, abspath)
+	}
+	if filepath.IsAbs(abspath) && abspath != filepath.Clean(abspath) {
+		t.Errorf(`Abs("")=%q, isn't clean`, 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`},
+	{`C:\Projects`, `c:\projects\src`, `src`},
+	{`C:\Projects`, `c:\projects`, `.`},
+	{`C:\Projects\a\..`, `c:\projects`, `.`},
+}
+
+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) { // https://golang.org/issue/3486
+	if runtime.GOOS == "ios" {
+		t.Skipf("skipping on %s/%s", runtime.GOOS, runtime.GOARCH)
+	}
+	root, err := filepath.EvalSymlinks(runtime.GOROOT() + "/test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	bugs := filepath.Join(root, "fixedbugs")
+	ken := filepath.Join(root, "ken")
+	seenBugs := false
+	seenKen := false
+	err = filepath.Walk(root, func(pth string, info fs.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 fixedbugs")
+			}
+			seenKen = true
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !seenKen {
+		t.Fatalf("%q not seen", ken)
+	}
+}
+
+func testWalkSymlink(t *testing.T, mklink func(target, link string) error) {
+	tmpdir, err := os.MkdirTemp("", "testWalkSymlink")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(wd)
+
+	err = os.Chdir(tmpdir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = mklink(tmpdir, "link")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var visited []string
+	err = filepath.Walk(tmpdir, func(path string, info fs.FileInfo, err error) error {
+		if err != nil {
+			t.Fatal(err)
+		}
+		rel, err := filepath.Rel(tmpdir, path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		visited = append(visited, rel)
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	sort.Strings(visited)
+	want := []string{".", "link"}
+	if fmt.Sprintf("%q", visited) != fmt.Sprintf("%q", want) {
+		t.Errorf("unexpected paths visited %q, want %q", visited, want)
+	}
+}
+
+func TestWalkSymlink(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+	testWalkSymlink(t, os.Symlink)
+}
+
+func TestIssue29372(t *testing.T) {
+	tmpDir, err := os.MkdirTemp("", "TestIssue29372")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	path := filepath.Join(tmpDir, "file.txt")
+	err = os.WriteFile(path, nil, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pathSeparator := string(filepath.Separator)
+	tests := []string{
+		path + strings.Repeat(pathSeparator, 1),
+		path + strings.Repeat(pathSeparator, 2),
+		path + strings.Repeat(pathSeparator, 1) + ".",
+		path + strings.Repeat(pathSeparator, 2) + ".",
+		path + strings.Repeat(pathSeparator, 1) + "..",
+		path + strings.Repeat(pathSeparator, 2) + "..",
+	}
+
+	for i, test := range tests {
+		_, err = filepath.EvalSymlinks(test)
+		if err != syscall.ENOTDIR {
+			t.Fatalf("test#%d: want %q, got %q", i, syscall.ENOTDIR, err)
+		}
+	}
+}
+
+// Issue 30520 part 1.
+func TestEvalSymlinksAboveRoot(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	t.Parallel()
+
+	tmpDir, err := os.MkdirTemp("", "TestEvalSymlinksAboveRoot")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	evalTmpDir, err := filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := os.Mkdir(filepath.Join(evalTmpDir, "a"), 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(filepath.Join(evalTmpDir, "a"), filepath.Join(evalTmpDir, "b")); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(evalTmpDir, "a", "file"), nil, 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	// Count the number of ".." elements to get to the root directory.
+	vol := filepath.VolumeName(evalTmpDir)
+	c := strings.Count(evalTmpDir[len(vol):], string(os.PathSeparator))
+	var dd []string
+	for i := 0; i < c+2; i++ {
+		dd = append(dd, "..")
+	}
+
+	wantSuffix := strings.Join([]string{"a", "file"}, string(os.PathSeparator))
+
+	// Try different numbers of "..".
+	for _, i := range []int{c, c + 1, c + 2} {
+		check := strings.Join([]string{evalTmpDir, strings.Join(dd[:i], string(os.PathSeparator)), evalTmpDir[len(vol)+1:], "b", "file"}, string(os.PathSeparator))
+		if resolved, err := filepath.EvalSymlinks(check); err != nil {
+			t.Errorf("EvalSymlinks(%q) failed: %v", check, err)
+		} else if !strings.HasSuffix(resolved, wantSuffix) {
+			t.Errorf("EvalSymlinks(%q) = %q does not end with %q", check, resolved, wantSuffix)
+		} else {
+			t.Logf("EvalSymlinks(%q) = %q", check, resolved)
+		}
+	}
+}
+
+// Issue 30520 part 2.
+func TestEvalSymlinksAboveRootChdir(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir, err := os.MkdirTemp("", "TestEvalSymlinksAboveRootChdir")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(wd)
+
+	if err := os.Chdir(tmpDir); err != nil {
+		t.Fatal(err)
+	}
+
+	subdir := filepath.Join("a", "b")
+	if err := os.MkdirAll(subdir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(subdir, "c"); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(subdir, "file"), nil, 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	subdir = filepath.Join("d", "e", "f")
+	if err := os.MkdirAll(subdir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Chdir(subdir); err != nil {
+		t.Fatal(err)
+	}
+
+	check := filepath.Join("..", "..", "..", "c", "file")
+	wantSuffix := filepath.Join("a", "b", "file")
+	if resolved, err := filepath.EvalSymlinks(check); err != nil {
+		t.Errorf("EvalSymlinks(%q) failed: %v", check, err)
+	} else if !strings.HasSuffix(resolved, wantSuffix) {
+		t.Errorf("EvalSymlinks(%q) = %q does not end with %q", check, resolved, wantSuffix)
+	} else {
+		t.Logf("EvalSymlinks(%q) = %q", check, resolved)
+	}
+}
diff --git a/src/path/filepath/path_unix.go b/src/path/filepath/path_unix.go
new file mode 100644
index 0000000..ec497d9
--- /dev/null
+++ b/src/path/filepath/path_unix.go
@@ -0,0 +1,53 @@
+// 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 aix darwin dragonfly freebsd js,wasm linux netbsd openbsd solaris
+
+package filepath
+
+import "strings"
+
+// IsAbs reports whether 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.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
+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)
+}
+
+func join(elem []string) string {
+	// If there's a bug here, fix the logic in ./path_plan9.go too.
+	for i, e := range elem {
+		if e != "" {
+			return Clean(strings.Join(elem[i:], string(Separator)))
+		}
+	}
+	return ""
+}
+
+func sameWord(a, b string) bool {
+	return a == b
+}
diff --git a/src/path/filepath/path_windows.go b/src/path/filepath/path_windows.go
new file mode 100644
index 0000000..445c868
--- /dev/null
+++ b/src/path/filepath/path_windows.go
@@ -0,0 +1,200 @@
+// 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 == '/'
+}
+
+// reservedNames lists reserved Windows names. Search for PRN in
+// https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file
+// for details.
+var reservedNames = []string{
+	"CON", "PRN", "AUX", "NUL",
+	"COM1", "COM2", "COM3", "COM4", "COM5", "COM6", "COM7", "COM8", "COM9",
+	"LPT1", "LPT2", "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9",
+}
+
+// isReservedName returns true, if path is Windows reserved name.
+// See reservedNames for the full list.
+func isReservedName(path string) bool {
+	if len(path) == 0 {
+		return false
+	}
+	for _, reserved := range reservedNames {
+		if strings.EqualFold(path, reserved) {
+			return true
+		}
+	}
+	return false
+}
+
+// IsAbs reports whether the path is absolute.
+func IsAbs(path string) (b bool) {
+	if isReservedName(path) {
+		return true
+	}
+	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? https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
+	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.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
+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 {
+		list[i] = strings.ReplaceAll(s, `"`, ``)
+	}
+
+	return list
+}
+
+func abs(path string) (string, error) {
+	if path == "" {
+		// syscall.FullPath returns an error on empty path, because it's not a valid path.
+		// To implement Abs behavior of returning working directory on empty string input,
+		// special-case empty path by changing it to "." path. See golang.org/issue/24441.
+		path = "."
+	}
+	fullPath, err := syscall.FullPath(path)
+	if err != nil {
+		return "", err
+	}
+	return Clean(fullPath), nil
+}
+
+func join(elem []string) string {
+	for i, e := range elem {
+		if e != "" {
+			return joinNonEmpty(elem[i:])
+		}
+	}
+	return ""
+}
+
+// joinNonEmpty is like join, but it assumes that the first element is non-empty.
+func joinNonEmpty(elem []string) string {
+	if len(elem[0]) == 2 && elem[0][1] == ':' {
+		// First element is drive letter without terminating slash.
+		// Keep path relative to current directory on that drive.
+		// Skip empty elements.
+		i := 1
+		for ; i < len(elem); i++ {
+			if elem[i] != "" {
+				break
+			}
+		}
+		return Clean(elem[0] + strings.Join(elem[i:], string(Separator)))
+	}
+	// The following logic prevents Join from inadvertently creating a
+	// UNC path on Windows. Unless the first element is a UNC path, Join
+	// shouldn't create a UNC path. See golang.org/issue/9167.
+	p := Clean(strings.Join(elem, string(Separator)))
+	if !isUNC(p) {
+		return p
+	}
+	// p == UNC only allowed when the first element is a UNC path.
+	head := Clean(elem[0])
+	if isUNC(head) {
+		return p
+	}
+	// head + tail == UNC, but joining two non-UNC paths should not result
+	// in a UNC path. Undo creation of UNC path.
+	tail := Clean(strings.Join(elem[1:], string(Separator)))
+	if head[len(head)-1] == Separator {
+		return head + tail
+	}
+	return head + string(Separator) + tail
+}
+
+// isUNC reports whether path is a UNC path.
+func isUNC(path string) bool {
+	return volumeNameLen(path) > 2
+}
+
+func sameWord(a, b string) bool {
+	return strings.EqualFold(a, b)
+}
diff --git a/src/path/filepath/path_windows_test.go b/src/path/filepath/path_windows_test.go
new file mode 100644
index 0000000..1c3d84c
--- /dev/null
+++ b/src/path/filepath/path_windows_test.go
@@ -0,0 +1,586 @@
+// 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 (
+	"flag"
+	"fmt"
+	"internal/testenv"
+	"io/fs"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"reflect"
+	"runtime/debug"
+	"strings"
+	"testing"
+)
+
+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    fs.FileMode = 0700
+	)
+
+	tmp, err := os.MkdirTemp("", "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 = os.WriteFile(fn, data, perm); err != nil {
+			t.Errorf("%d,%d: WriteFile(%#q) failed: %v", ti, i, fn, err)
+			return
+		}
+	}
+
+	// on some systems, SystemRoot is required for cmd to work
+	systemRoot := os.Getenv("SystemRoot")
+
+	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=` + systemRoot + "/System32;" + tt.list, `SystemRoot=` + systemRoot},
+			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)
+			}
+		}
+	}
+}
+
+func TestWindowsEvalSymlinks(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir, err := os.MkdirTemp("", "TestWindowsEvalSymlinks")
+	if err != nil {
+		t.Fatal(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(err)
+	}
+
+	if len(tmpDir) < 3 {
+		t.Fatalf("tmpDir path %q is too short", tmpDir)
+	}
+	if tmpDir[1] != ':' {
+		t.Fatalf("tmpDir path %q must have drive letter in it", tmpDir)
+	}
+	test := EvalSymlinksTest{"test/linkabswin", tmpDir[:3]}
+
+	// Create the symlink farm using relative paths.
+	testdirs := append(EvalSymlinksTestDirs, test)
+	for _, d := range testdirs {
+		var err error
+		path := simpleJoin(tmpDir, d.path)
+		if d.dest == "" {
+			err = os.Mkdir(path, 0755)
+		} else {
+			err = os.Symlink(d.dest, path)
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	path := simpleJoin(tmpDir, test.path)
+
+	testEvalSymlinks(t, path, test.dest)
+
+	testEvalSymlinksAfterChdir(t, path, ".", test.dest)
+
+	testEvalSymlinksAfterChdir(t,
+		path,
+		filepath.VolumeName(tmpDir)+".",
+		test.dest)
+
+	testEvalSymlinksAfterChdir(t,
+		simpleJoin(tmpDir, "test"),
+		simpleJoin("..", test.path),
+		test.dest)
+
+	testEvalSymlinksAfterChdir(t, tmpDir, test.path, test.dest)
+}
+
+// TestEvalSymlinksCanonicalNames verify that EvalSymlinks
+// returns "canonical" path names on windows.
+func TestEvalSymlinksCanonicalNames(t *testing.T) {
+	tmp, err := os.MkdirTemp("", "evalsymlinkcanonical")
+	if err != nil {
+		t.Fatal("creating temp dir:", err)
+	}
+	defer os.RemoveAll(tmp)
+
+	// os.MkdirTemp might return "non-canonical" name.
+	cTmpName, err := filepath.EvalSymlinks(tmp)
+	if err != nil {
+		t.Errorf("EvalSymlinks(%q) error: %v", tmp, err)
+	}
+
+	dirs := []string{
+		"test",
+		"test/dir",
+		"testing_long_dir",
+		"TEST2",
+	}
+
+	for _, d := range dirs {
+		dir := filepath.Join(cTmpName, d)
+		err := os.Mkdir(dir, 0755)
+		if err != nil {
+			t.Fatal(err)
+		}
+		cname, err := filepath.EvalSymlinks(dir)
+		if err != nil {
+			t.Errorf("EvalSymlinks(%q) error: %v", dir, err)
+			continue
+		}
+		if dir != cname {
+			t.Errorf("EvalSymlinks(%q) returns %q, but should return %q", dir, cname, dir)
+			continue
+		}
+		// test non-canonical names
+		test := strings.ToUpper(dir)
+		p, err := filepath.EvalSymlinks(test)
+		if err != nil {
+			t.Errorf("EvalSymlinks(%q) error: %v", test, err)
+			continue
+		}
+		if p != cname {
+			t.Errorf("EvalSymlinks(%q) returns %q, but should return %q", test, p, cname)
+			continue
+		}
+		// another test
+		test = strings.ToLower(dir)
+		p, err = filepath.EvalSymlinks(test)
+		if err != nil {
+			t.Errorf("EvalSymlinks(%q) error: %v", test, err)
+			continue
+		}
+		if p != cname {
+			t.Errorf("EvalSymlinks(%q) returns %q, but should return %q", test, p, cname)
+			continue
+		}
+	}
+}
+
+// checkVolume8dot3Setting runs "fsutil 8dot3name query c:" command
+// (where c: is vol parameter) to discover "8dot3 name creation state".
+// The state is combination of 2 flags. The global flag controls if it
+// is per volume or global setting:
+//   0 - Enable 8dot3 name creation on all volumes on the system
+//   1 - Disable 8dot3 name creation on all volumes on the system
+//   2 - Set 8dot3 name creation on a per volume basis
+//   3 - Disable 8dot3 name creation on all volumes except the system volume
+// If global flag is set to 2, then per-volume flag needs to be examined:
+//   0 - Enable 8dot3 name creation on this volume
+//   1 - Disable 8dot3 name creation on this volume
+// checkVolume8dot3Setting verifies that "8dot3 name creation" flags
+// are set to 2 and 0, if enabled parameter is true, or 2 and 1, if enabled
+// is false. Otherwise checkVolume8dot3Setting returns error.
+func checkVolume8dot3Setting(vol string, enabled bool) error {
+	// It appears, on some systems "fsutil 8dot3name query ..." command always
+	// exits with error. Ignore exit code, and look at fsutil output instead.
+	out, _ := exec.Command("fsutil", "8dot3name", "query", vol).CombinedOutput()
+	// Check that system has "Volume level setting" set.
+	expected := "The registry state of NtfsDisable8dot3NameCreation is 2, the default (Volume level setting)"
+	if !strings.Contains(string(out), expected) {
+		// Windows 10 version of fsutil has different output message.
+		expectedWindow10 := "The registry state is: 2 (Per volume setting - the default)"
+		if !strings.Contains(string(out), expectedWindow10) {
+			return fmt.Errorf("fsutil output should contain %q, but is %q", expected, string(out))
+		}
+	}
+	// Now check the volume setting.
+	expected = "Based on the above two settings, 8dot3 name creation is %s on %s"
+	if enabled {
+		expected = fmt.Sprintf(expected, "enabled", vol)
+	} else {
+		expected = fmt.Sprintf(expected, "disabled", vol)
+	}
+	if !strings.Contains(string(out), expected) {
+		return fmt.Errorf("unexpected fsutil output: %q", string(out))
+	}
+	return nil
+}
+
+func setVolume8dot3Setting(vol string, enabled bool) error {
+	cmd := []string{"fsutil", "8dot3name", "set", vol}
+	if enabled {
+		cmd = append(cmd, "0")
+	} else {
+		cmd = append(cmd, "1")
+	}
+	// It appears, on some systems "fsutil 8dot3name set ..." command always
+	// exits with error. Ignore exit code, and look at fsutil output instead.
+	out, _ := exec.Command(cmd[0], cmd[1:]...).CombinedOutput()
+	if string(out) != "\r\nSuccessfully set 8dot3name behavior.\r\n" {
+		// Windows 10 version of fsutil has different output message.
+		expectedWindow10 := "Successfully %s 8dot3name generation on %s\r\n"
+		if enabled {
+			expectedWindow10 = fmt.Sprintf(expectedWindow10, "enabled", vol)
+		} else {
+			expectedWindow10 = fmt.Sprintf(expectedWindow10, "disabled", vol)
+		}
+		if string(out) != expectedWindow10 {
+			return fmt.Errorf("%v command failed: %q", cmd, string(out))
+		}
+	}
+	return nil
+}
+
+var runFSModifyTests = flag.Bool("run_fs_modify_tests", false, "run tests which modify filesystem parameters")
+
+// This test assumes registry state of NtfsDisable8dot3NameCreation is 2,
+// the default (Volume level setting).
+func TestEvalSymlinksCanonicalNamesWith8dot3Disabled(t *testing.T) {
+	if !*runFSModifyTests {
+		t.Skip("skipping test that modifies file system setting; enable with -run_fs_modify_tests")
+	}
+	tempVol := filepath.VolumeName(os.TempDir())
+	if len(tempVol) != 2 {
+		t.Fatalf("unexpected temp volume name %q", tempVol)
+	}
+
+	err := checkVolume8dot3Setting(tempVol, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = setVolume8dot3Setting(tempVol, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := setVolume8dot3Setting(tempVol, true)
+		if err != nil {
+			t.Fatal(err)
+		}
+		err = checkVolume8dot3Setting(tempVol, true)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+	err = checkVolume8dot3Setting(tempVol, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	TestEvalSymlinksCanonicalNames(t)
+}
+
+func TestToNorm(t *testing.T) {
+	stubBase := func(path string) (string, error) {
+		vol := filepath.VolumeName(path)
+		path = path[len(vol):]
+
+		if strings.Contains(path, "/") {
+			return "", fmt.Errorf("invalid path is given to base: %s", vol+path)
+		}
+
+		if path == "" || path == "." || path == `\` {
+			return "", fmt.Errorf("invalid path is given to base: %s", vol+path)
+		}
+
+		i := strings.LastIndexByte(path, filepath.Separator)
+		if i == len(path)-1 { // trailing '\' is invalid
+			return "", fmt.Errorf("invalid path is given to base: %s", vol+path)
+		}
+		if i == -1 {
+			return strings.ToUpper(path), nil
+		}
+
+		return strings.ToUpper(path[i+1:]), nil
+	}
+
+	// On this test, toNorm should be same as string.ToUpper(filepath.Clean(path)) except empty string.
+	tests := []struct {
+		arg  string
+		want string
+	}{
+		{"", ""},
+		{".", "."},
+		{"./foo/bar", `FOO\BAR`},
+		{"/", `\`},
+		{"/foo/bar", `\FOO\BAR`},
+		{"/foo/bar/baz/qux", `\FOO\BAR\BAZ\QUX`},
+		{"foo/bar", `FOO\BAR`},
+		{"C:/foo/bar", `C:\FOO\BAR`},
+		{"C:foo/bar", `C:FOO\BAR`},
+		{"c:/foo/bar", `C:\FOO\BAR`},
+		{"C:/foo/bar", `C:\FOO\BAR`},
+		{"C:/foo/bar/", `C:\FOO\BAR`},
+		{`C:\foo\bar`, `C:\FOO\BAR`},
+		{`C:\foo/bar\`, `C:\FOO\BAR`},
+		{"C:/ふー/バー", `C:\ふー\バー`},
+	}
+
+	for _, test := range tests {
+		got, err := filepath.ToNorm(test.arg, stubBase)
+		if err != nil {
+			t.Errorf("toNorm(%s) failed: %v\n", test.arg, err)
+		} else if got != test.want {
+			t.Errorf("toNorm(%s) returns %s, but %s expected\n", test.arg, got, test.want)
+		}
+	}
+
+	testPath := `{{tmp}}\test\foo\bar`
+
+	testsDir := []struct {
+		wd   string
+		arg  string
+		want string
+	}{
+		// test absolute paths
+		{".", `{{tmp}}\test\foo\bar`, `{{tmp}}\test\foo\bar`},
+		{".", `{{tmp}}\.\test/foo\bar`, `{{tmp}}\test\foo\bar`},
+		{".", `{{tmp}}\test\..\test\foo\bar`, `{{tmp}}\test\foo\bar`},
+		{".", `{{tmp}}\TEST\FOO\BAR`, `{{tmp}}\test\foo\bar`},
+
+		// test relative paths begin with drive letter
+		{`{{tmp}}\test`, `{{tmpvol}}.`, `{{tmpvol}}.`},
+		{`{{tmp}}\test`, `{{tmpvol}}..`, `{{tmpvol}}..`},
+		{`{{tmp}}\test`, `{{tmpvol}}foo\bar`, `{{tmpvol}}foo\bar`},
+		{`{{tmp}}\test`, `{{tmpvol}}.\foo\bar`, `{{tmpvol}}foo\bar`},
+		{`{{tmp}}\test`, `{{tmpvol}}foo\..\foo\bar`, `{{tmpvol}}foo\bar`},
+		{`{{tmp}}\test`, `{{tmpvol}}FOO\BAR`, `{{tmpvol}}foo\bar`},
+
+		// test relative paths begin with '\'
+		{"{{tmp}}", `{{tmpnovol}}\test\foo\bar`, `{{tmpnovol}}\test\foo\bar`},
+		{"{{tmp}}", `{{tmpnovol}}\.\test\foo\bar`, `{{tmpnovol}}\test\foo\bar`},
+		{"{{tmp}}", `{{tmpnovol}}\test\..\test\foo\bar`, `{{tmpnovol}}\test\foo\bar`},
+		{"{{tmp}}", `{{tmpnovol}}\TEST\FOO\BAR`, `{{tmpnovol}}\test\foo\bar`},
+
+		// test relative paths begin without '\'
+		{`{{tmp}}\test`, ".", `.`},
+		{`{{tmp}}\test`, "..", `..`},
+		{`{{tmp}}\test`, `foo\bar`, `foo\bar`},
+		{`{{tmp}}\test`, `.\foo\bar`, `foo\bar`},
+		{`{{tmp}}\test`, `foo\..\foo\bar`, `foo\bar`},
+		{`{{tmp}}\test`, `FOO\BAR`, `foo\bar`},
+
+		// test UNC paths
+		{".", `\\localhost\c$`, `\\localhost\c$`},
+	}
+
+	tmp, err := os.MkdirTemp("", "testToNorm")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := os.RemoveAll(tmp)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	// os.MkdirTemp might return "non-canonical" name.
+	ctmp, err := filepath.EvalSymlinks(tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = os.MkdirAll(strings.ReplaceAll(testPath, "{{tmp}}", ctmp), 0777)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := os.Chdir(cwd)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	tmpVol := filepath.VolumeName(ctmp)
+	if len(tmpVol) != 2 {
+		t.Fatalf("unexpected temp volume name %q", tmpVol)
+	}
+
+	tmpNoVol := ctmp[len(tmpVol):]
+
+	replacer := strings.NewReplacer("{{tmp}}", ctmp, "{{tmpvol}}", tmpVol, "{{tmpnovol}}", tmpNoVol)
+
+	for _, test := range testsDir {
+		wd := replacer.Replace(test.wd)
+		arg := replacer.Replace(test.arg)
+		want := replacer.Replace(test.want)
+
+		if test.wd == "." {
+			err := os.Chdir(cwd)
+			if err != nil {
+				t.Error(err)
+
+				continue
+			}
+		} else {
+			err := os.Chdir(wd)
+			if err != nil {
+				t.Error(err)
+
+				continue
+			}
+		}
+
+		got, err := filepath.ToNorm(arg, filepath.NormBase)
+		if err != nil {
+			t.Errorf("toNorm(%s) failed: %v (wd=%s)\n", arg, err, wd)
+		} else if got != want {
+			t.Errorf("toNorm(%s) returns %s, but %s expected (wd=%s)\n", arg, got, want, wd)
+		}
+	}
+}
+
+func TestUNC(t *testing.T) {
+	// Test that this doesn't go into an infinite recursion.
+	// See golang.org/issue/15879.
+	defer debug.SetMaxStack(debug.SetMaxStack(1e6))
+	filepath.Glob(`\\?\c:\*`)
+}
+
+func testWalkMklink(t *testing.T, linktype string) {
+	output, _ := exec.Command("cmd", "/c", "mklink", "/?").Output()
+	if !strings.Contains(string(output), fmt.Sprintf(" /%s ", linktype)) {
+		t.Skipf(`skipping test; mklink does not supports /%s parameter`, linktype)
+	}
+	testWalkSymlink(t, func(target, link string) error {
+		output, err := exec.Command("cmd", "/c", "mklink", "/"+linktype, link, target).CombinedOutput()
+		if err != nil {
+			return fmt.Errorf(`"mklink /%s %v %v" command failed: %v\n%v`, linktype, link, target, err, string(output))
+		}
+		return nil
+	})
+}
+
+func TestWalkDirectoryJunction(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+	testWalkMklink(t, "J")
+}
+
+func TestWalkDirectorySymlink(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+	testWalkMklink(t, "D")
+}
+
+func TestNTNamespaceSymlink(t *testing.T) {
+	output, _ := exec.Command("cmd", "/c", "mklink", "/?").Output()
+	if !strings.Contains(string(output), " /J ") {
+		t.Skip("skipping test because mklink command does not support junctions")
+	}
+
+	tmpdir, err := os.MkdirTemp("", "TestNTNamespaceSymlink")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	// Make sure tmpdir is not a symlink, otherwise tests will fail.
+	tmpdir, err = filepath.EvalSymlinks(tmpdir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	vol := filepath.VolumeName(tmpdir)
+	output, err = exec.Command("cmd", "/c", "mountvol", vol, "/L").CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to run mountvol %v /L: %v %q", vol, err, output)
+	}
+	target := strings.Trim(string(output), " \n\r")
+
+	dirlink := filepath.Join(tmpdir, "dirlink")
+	output, err = exec.Command("cmd", "/c", "mklink", "/J", dirlink, target).CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to run mklink %v %v: %v %q", dirlink, target, err, output)
+	}
+
+	got, err := filepath.EvalSymlinks(dirlink)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := vol + `\`; got != want {
+		t.Errorf(`EvalSymlinks(%q): got %q, want %q`, dirlink, got, want)
+	}
+
+	// Make sure we have sufficient privilege to run mklink command.
+	testenv.MustHaveSymlink(t)
+
+	file := filepath.Join(tmpdir, "file")
+	err = os.WriteFile(file, []byte(""), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	target += file[len(filepath.VolumeName(file)):]
+
+	filelink := filepath.Join(tmpdir, "filelink")
+	output, err = exec.Command("cmd", "/c", "mklink", filelink, target).CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to run mklink %v %v: %v %q", filelink, target, err, output)
+	}
+
+	got, err = filepath.EvalSymlinks(filelink)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := file; got != want {
+		t.Errorf(`EvalSymlinks(%q): got %q, want %q`, filelink, got, want)
+	}
+}
diff --git a/src/path/filepath/symlink.go b/src/path/filepath/symlink.go
new file mode 100644
index 0000000..6fefd15
--- /dev/null
+++ b/src/path/filepath/symlink.go
@@ -0,0 +1,147 @@
+// 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 (
+	"errors"
+	"io/fs"
+	"os"
+	"runtime"
+	"syscall"
+)
+
+func walkSymlinks(path string) (string, error) {
+	volLen := volumeNameLen(path)
+	pathSeparator := string(os.PathSeparator)
+
+	if volLen < len(path) && os.IsPathSeparator(path[volLen]) {
+		volLen++
+	}
+	vol := path[:volLen]
+	dest := vol
+	linksWalked := 0
+	for start, end := volLen, volLen; start < len(path); start = end {
+		for start < len(path) && os.IsPathSeparator(path[start]) {
+			start++
+		}
+		end = start
+		for end < len(path) && !os.IsPathSeparator(path[end]) {
+			end++
+		}
+
+		// On Windows, "." can be a symlink.
+		// We look it up, and use the value if it is absolute.
+		// If not, we just return ".".
+		isWindowsDot := runtime.GOOS == "windows" && path[volumeNameLen(path):] == "."
+
+		// The next path component is in path[start:end].
+		if end == start {
+			// No more path components.
+			break
+		} else if path[start:end] == "." && !isWindowsDot {
+			// Ignore path component ".".
+			continue
+		} else if path[start:end] == ".." {
+			// Back up to previous component if possible.
+			// Note that volLen includes any leading slash.
+
+			// Set r to the index of the last slash in dest,
+			// after the volume.
+			var r int
+			for r = len(dest) - 1; r >= volLen; r-- {
+				if os.IsPathSeparator(dest[r]) {
+					break
+				}
+			}
+			if r < volLen || dest[r+1:] == ".." {
+				// Either path has no slashes
+				// (it's empty or just "C:")
+				// or it ends in a ".." we had to keep.
+				// Either way, keep this "..".
+				if len(dest) > volLen {
+					dest += pathSeparator
+				}
+				dest += ".."
+			} else {
+				// Discard everything since the last slash.
+				dest = dest[:r]
+			}
+			continue
+		}
+
+		// Ordinary path component. Add it to result.
+
+		if len(dest) > volumeNameLen(dest) && !os.IsPathSeparator(dest[len(dest)-1]) {
+			dest += pathSeparator
+		}
+
+		dest += path[start:end]
+
+		// Resolve symlink.
+
+		fi, err := os.Lstat(dest)
+		if err != nil {
+			return "", err
+		}
+
+		if fi.Mode()&fs.ModeSymlink == 0 {
+			if !fi.Mode().IsDir() && end < len(path) {
+				return "", syscall.ENOTDIR
+			}
+			continue
+		}
+
+		// Found symlink.
+
+		linksWalked++
+		if linksWalked > 255 {
+			return "", errors.New("EvalSymlinks: too many links")
+		}
+
+		link, err := os.Readlink(dest)
+		if err != nil {
+			return "", err
+		}
+
+		if isWindowsDot && !IsAbs(link) {
+			// On Windows, if "." is a relative symlink,
+			// just return ".".
+			break
+		}
+
+		path = link + path[end:]
+
+		v := volumeNameLen(link)
+		if v > 0 {
+			// Symlink to drive name is an absolute path.
+			if v < len(link) && os.IsPathSeparator(link[v]) {
+				v++
+			}
+			vol = link[:v]
+			dest = vol
+			end = len(vol)
+		} else if len(link) > 0 && os.IsPathSeparator(link[0]) {
+			// Symlink to absolute path.
+			dest = link[:1]
+			end = 1
+		} else {
+			// Symlink to relative path; replace last
+			// path component in dest.
+			var r int
+			for r = len(dest) - 1; r >= volLen; r-- {
+				if os.IsPathSeparator(dest[r]) {
+					break
+				}
+			}
+			if r < volLen {
+				dest = vol
+			} else {
+				dest = dest[:r]
+			}
+			end = 0
+		}
+	}
+	return Clean(dest), nil
+}
diff --git a/src/path/filepath/symlink_unix.go b/src/path/filepath/symlink_unix.go
new file mode 100644
index 0000000..d20e63a
--- /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 0000000..d72279e
--- /dev/null
+++ b/src/path/filepath/symlink_windows.go
@@ -0,0 +1,119 @@
+// 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 (
+	"strings"
+	"syscall"
+)
+
+// normVolumeName is like VolumeName, but makes drive letter upper case.
+// result of EvalSymlinks must be unique, so we have
+// EvalSymlinks(`c:\a`) == EvalSymlinks(`C:\a`).
+func normVolumeName(path string) string {
+	volume := VolumeName(path)
+
+	if len(volume) > 2 { // isUNC
+		return volume
+	}
+
+	return strings.ToUpper(volume)
+}
+
+// normBase returns the last element of path with correct case.
+func normBase(path string) (string, error) {
+	p, err := syscall.UTF16PtrFromString(path)
+	if err != nil {
+		return "", err
+	}
+
+	var data syscall.Win32finddata
+
+	h, err := syscall.FindFirstFile(p, &data)
+	if err != nil {
+		return "", err
+	}
+	syscall.FindClose(h)
+
+	return syscall.UTF16ToString(data.FileName[:]), nil
+}
+
+// baseIsDotDot reports whether the last element of path is "..".
+// The given path should be 'Clean'-ed in advance.
+func baseIsDotDot(path string) bool {
+	i := strings.LastIndexByte(path, Separator)
+	return path[i+1:] == ".."
+}
+
+// toNorm returns the normalized path that is guaranteed to be unique.
+// It should accept the following formats:
+//   * UNC paths                              (e.g \\server\share\foo\bar)
+//   * absolute paths                         (e.g C:\foo\bar)
+//   * relative paths begin with drive letter (e.g C:foo\bar, C:..\foo\bar, C:.., C:.)
+//   * relative paths begin with '\'          (e.g \foo\bar)
+//   * relative paths begin without '\'       (e.g foo\bar, ..\foo\bar, .., .)
+// The returned normalized path will be in the same form (of 5 listed above) as the input path.
+// If two paths A and B are indicating the same file with the same format, toNorm(A) should be equal to toNorm(B).
+// The normBase parameter should be equal to the normBase func, except for in tests.  See docs on the normBase func.
+func toNorm(path string, normBase func(string) (string, error)) (string, error) {
+	if path == "" {
+		return path, nil
+	}
+
+	path = Clean(path)
+
+	volume := normVolumeName(path)
+	path = path[len(volume):]
+
+	// skip special cases
+	if path == "" || path == "." || path == `\` {
+		return volume + path, nil
+	}
+
+	var normPath string
+
+	for {
+		if baseIsDotDot(path) {
+			normPath = path + `\` + normPath
+
+			break
+		}
+
+		name, err := normBase(volume + path)
+		if err != nil {
+			return "", err
+		}
+
+		normPath = name + `\` + normPath
+
+		i := strings.LastIndexByte(path, Separator)
+		if i == -1 {
+			break
+		}
+		if i == 0 { // `\Go` or `C:\Go`
+			normPath = `\` + normPath
+
+			break
+		}
+
+		path = path[:i]
+	}
+
+	normPath = normPath[:len(normPath)-1] // remove trailing '\'
+
+	return volume + normPath, nil
+}
+
+func evalSymlinks(path string) (string, error) {
+	newpath, err := walkSymlinks(path)
+	if err != nil {
+		return "", err
+	}
+	newpath, err = toNorm(newpath, normBase)
+	if err != nil {
+		return "", err
+	}
+	return newpath, nil
+}
diff --git a/src/path/match.go b/src/path/match.go
new file mode 100644
index 0000000..918624c
--- /dev/null
+++ b/src/path/match.go
@@ -0,0 +1,231 @@
+// 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"
+	"internal/bytealg"
+	"unicode/utf8"
+)
+
+// ErrBadPattern indicates a pattern was malformed.
+var ErrBadPattern = errors.New("syntax error in pattern")
+
+// Match reports whether name matches the shell 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 bytealg.IndexByteString(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
+				}
+			}
+		}
+		// Before returning false with no error,
+		// check that the remainder of the pattern is syntactically valid.
+		for len(pattern) > 0 {
+			_, chunk, pattern = scanChunk(pattern)
+			if _, _, err := matchChunk(chunk, ""); 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) {
+	// failed records whether the match has failed.
+	// After the match fails, the loop continues on processing chunk,
+	// checking that the pattern is well-formed but no longer reading s.
+	failed := false
+	for len(chunk) > 0 {
+		if !failed && len(s) == 0 {
+			failed = true
+		}
+		switch chunk[0] {
+		case '[':
+			// character class
+			var r rune
+			if !failed {
+				var n int
+				r, n = utf8.DecodeRuneInString(s)
+				s = s[n:]
+			}
+			chunk = chunk[1:]
+			// possibly negated
+			negated := false
+			if len(chunk) > 0 && chunk[0] == '^' {
+				negated = true
+				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 "", false, err
+				}
+				hi = lo
+				if chunk[0] == '-' {
+					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
+						return "", false, err
+					}
+				}
+				if lo <= r && r <= hi {
+					match = true
+				}
+				nrange++
+			}
+			if match == negated {
+				failed = true
+			}
+
+		case '?':
+			if !failed {
+				if s[0] == '/' {
+					failed = true
+				}
+				_, n := utf8.DecodeRuneInString(s)
+				s = s[n:]
+			}
+			chunk = chunk[1:]
+
+		case '\\':
+			chunk = chunk[1:]
+			if len(chunk) == 0 {
+				return "", false, ErrBadPattern
+			}
+			fallthrough
+
+		default:
+			if !failed {
+				if chunk[0] != s[0] {
+					failed = true
+				}
+				s = s[1:]
+			}
+			chunk = chunk[1:]
+		}
+	}
+	if failed {
+		return "", false, nil
+	}
+	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 0000000..996bd69
--- /dev/null
+++ b/src/path/match_test.go
@@ -0,0 +1,84 @@
+// 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_test
+
+import (
+	. "path"
+	"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, ErrBadPattern},
+	{"a[", "ab", false, ErrBadPattern},
+	{"a[", "x", false, ErrBadPattern},
+	{"a/b[", "x", 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, %v", tt.pattern, tt.s, ok, err, tt.match, tt.err)
+		}
+	}
+}
diff --git a/src/path/path.go b/src/path/path.go
new file mode 100644
index 0000000..f1f3499
--- /dev/null
+++ b/src/path/path.go
@@ -0,0 +1,233 @@
+// 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.
+//
+// The path package should only be used for paths separated by forward
+// slashes, such as the paths in URLs. This package does not deal with
+// Windows paths with drive letters or backslashes; to manipulate
+// operating system paths, use the path/filepath package.
+package path
+
+// 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,''
+// https://9p.io/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()
+}
+
+// lastSlash(s) is strings.LastIndex(s, "/") but we can't import strings.
+func lastSlash(s string) int {
+	i := len(s) - 1
+	for i >= 0 && s[i] != '/' {
+		i--
+	}
+	return i
+}
+
+// Split splits path immediately following the final slash,
+// separating it into a directory and file name component.
+// If there is no slash 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) {
+	i := lastSlash(path)
+	return path[:i+1], path[i+1:]
+}
+
+// Join joins any number of path elements into a single path,
+// separating them with slashes. Empty elements are ignored.
+// The result is Cleaned. However, if the argument list is
+// empty or all its elements are empty, Join returns
+// an empty string.
+func Join(elem ...string) string {
+	size := 0
+	for _, e := range elem {
+		size += len(e)
+	}
+	if size == 0 {
+		return ""
+	}
+	buf := make([]byte, 0, size+len(elem)-1)
+	for _, e := range elem {
+		if len(buf) > 0 || e != "" {
+			if len(buf) > 0 {
+				buf = append(buf, '/')
+			}
+			buf = append(buf, e...)
+		}
+	}
+	return Clean(string(buf))
+}
+
+// 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 := lastSlash(path); i >= 0 {
+		path = path[i+1:]
+	}
+	// If empty now, it had only slashes.
+	if path == "" {
+		return "/"
+	}
+	return path
+}
+
+// IsAbs reports whether 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 0000000..a57286f
--- /dev/null
+++ b/src/path/path_test.go
@@ -0,0 +1,236 @@
+// 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_test
+
+import (
+	. "path"
+	"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{"", ""}, ""},
+}
+
+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)
+		}
+	}
+}