os: fix FileInfo.Name returned by Stat

Fixes #1645.

R=rsc
CC=golang-dev
https://golang.org/cl/4321045

src/pkg/os/file_unix.go

@@ -102,3 +102,21 @@ func Truncate(name string, size int64) Error {
 	}
 	return nil
 }
+
+// basename removes trailing slashes and the leading directory name from path name
+func basename(name string) string {
+	i := len(name) - 1
+	// Remove trailing slashes
+	for ; i > 0 && name[i] == '/'; i-- {
+		name = name[:i]
+	}
+	// Remove leading directory name
+	for i--; i >= 0; i-- {
+		if name[i] == '/' {
+			name = name[i+1:]
+			break
+		}
+	}
+
+	return name
+}

src/pkg/os/stat_darwin.go

@@ -24,13 +24,7 @@ func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *F
 	fi.Atime_ns = syscall.TimespecToNsec(stat.Atimespec)
 	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtimespec)
 	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctimespec)
-	for i := len(name) - 1; i >= 0; i-- {
-		if name[i] == '/' {
-			name = name[i+1:]
-			break
-		}
-	}
-	fi.Name = name
+	fi.Name = basename(name)
 	if isSymlink(lstat) && !isSymlink(stat) {
 		fi.FollowedSymlink = true
 	}

src/pkg/os/stat_freebsd.go

@@ -24,13 +24,7 @@ func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *F
 	fi.Atime_ns = syscall.TimespecToNsec(stat.Atimespec)
 	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtimespec)
 	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctimespec)
-	for i := len(name) - 1; i >= 0; i-- {
-		if name[i] == '/' {
-			name = name[i+1:]
-			break
-		}
-	}
-	fi.Name = name
+	fi.Name = basename(name)
 	if isSymlink(lstat) && !isSymlink(stat) {
 		fi.FollowedSymlink = true
 	}

src/pkg/os/stat_linux.go

@@ -24,13 +24,7 @@ func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *F
 	fi.Atime_ns = syscall.TimespecToNsec(stat.Atim)
 	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtim)
 	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctim)
-	for i := len(name) - 1; i >= 0; i-- {
-		if name[i] == '/' {
-			name = name[i+1:]
-			break
-		}
-	}
-	fi.Name = name
+	fi.Name = basename(name)
 	if isSymlink(lstat) && !isSymlink(stat) {
 		fi.FollowedSymlink = true
 	}