getfile on windows: when a file cannot be symlinked because there is …

…no privilege, copy it

Symlinking allows to optimize the space taken by go-get in case the operation runs locally.
But running the go getter without the symlinking privilege can fail in this case.

This will copy the file instead of symlinking it in case we don't have the priviledge.

get_file_windows.go

@@ -9,6 +9,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"syscall"
 )
 
 func (g *FileGetter) Get(dst string, u *url.URL) error {
@@ -93,7 +94,21 @@ func (g *FileGetter) GetFile(dst string, u *url.URL) error {
 
 	// If we're not copying, just symlink and we're done
 	if !g.Copy {
-		return os.Symlink(path, dst)
+		if err = os.Symlink(path, dst); err == nil {
+			return err
+		}
+		lerr, ok := err.(*os.LinkError)
+		if !ok {
+			return err
+		}
+		switch lerr.Err {
+		case syscall.ERROR_PRIVILEGE_NOT_HELD:
+			// no symlink privilege, let's
+			// fallback to a copy to avoid an error.
+			break
+		default:
+			return err
+		}
 	}
 
 	// Copy