path, path/filepath: remove dead code

Fixes #8503.

Thanks to no.smile.face for the original report.

LGTM=bradfitz, r, ruiu
R=bradfitz, ruiu, r
CC=golang-codereviews
https://golang.org/cl/132730043

src/pkg/path/filepath/path.go

@@ -452,13 +452,6 @@ func Dir(path string) string {
 		i--
 	}
 	dir := Clean(path[len(vol) : i+1])
-	last := len(dir) - 1
-	if last > 0 && os.IsPathSeparator(dir[last]) {
-		dir = dir[:last]
-	}
-	if dir == "" {
-		dir = "."
-	}
 	return vol + dir
 }
 

src/pkg/path/path.go

@@ -206,13 +206,5 @@ func IsAbs(path string) bool {
 // slash.
 func Dir(path string) string {
 	dir, _ := Split(path)
-	dir = Clean(dir)
-	last := len(dir) - 1
-	if last > 0 && dir[last] == '/' {
-		dir = dir[:last]
-	}
-	if dir == "" {
-		dir = "."
-	}
-	return dir
+	return Clean(dir)
 }