exec.LookPath() unix/windows separation

R=brainman, rsc, vcc, rsc1
CC=golang-dev
https://golang.org/cl/2068041

src/pkg/exec/exec.go

@@ -7,7 +7,6 @@ package exec
 
 import (
 	"os"
-	"strings"
 )
 
 // Arguments to Run.
@@ -182,40 +181,3 @@ func (p *Cmd) Close() os.Error {
 	}
 	return err
 }
-
-func canExec(file string) bool {
-	d, err := os.Stat(file)
-	if err != nil {
-		return false
-	}
-	return d.IsRegular() && d.Permission()&0111 != 0
-}
-
-// LookPath searches for an executable binary named file
-// in the directories named by the PATH environment variable.
-// If file contains a slash, it is tried directly and the PATH is not consulted.
-//
-// TODO(rsc): Does LookPath belong in os instead?
-func LookPath(file string) (string, os.Error) {
-	// NOTE(rsc): I wish we could use the Plan 9 behavior here
-	// (only bypass the path if file begins with / or ./ or ../)
-	// but that would not match all the Unix shells.
-
-	if strings.Index(file, "/") >= 0 {
-		if canExec(file) {
-			return file, nil
-		}
-		return "", os.ENOENT
-	}
-	pathenv := os.Getenv("PATH")
-	for _, dir := range strings.Split(pathenv, ":", -1) {
-		if dir == "" {
-			// Unix shell semantics: path element "" means "."
-			dir = "."
-		}
-		if canExec(dir + "/" + file) {
-			return dir + "/" + file, nil
-		}
-	}
-	return "", os.ENOENT
-}