// +build linux
 
 package builder
 
 import (
 	"os"
 	"path/filepath"
 )
 
 func fixPermissions(source, destination string, uid, gid int, destExisted bool) error {
 	// If the destination didn't already exist, or the destination isn't a
 	// directory, then we should Lchown the destination. Otherwise, we shouldn't
 	// Lchown the destination.
 	destStat, err := os.Stat(destination)
 	if err != nil {
 		// This should *never* be reached, because the destination must've already
 		// been created while untar-ing the context.
 		return err
 	}
 	doChownDestination := !destExisted || !destStat.IsDir()
 
 	// We Walk on the source rather than on the destination because we don't
 	// want to change permissions on things we haven't created or modified.
 	return filepath.Walk(source, func(fullpath string, info os.FileInfo, err error) error {
 		// Do not alter the walk root iff. it existed before, as it doesn't fall under
 		// the domain of "things we should chown".
 		if !doChownDestination && (source == fullpath) {
 			return nil
 		}
 
 		// Path is prefixed by source: substitute with destination instead.
 		cleaned, err := filepath.Rel(source, fullpath)
 		if err != nil {
 			return err
 		}
 
 		fullpath = filepath.Join(destination, cleaned)
 		return os.Lchown(fullpath, uid, gid)
 	})
 }