Fixes for single/multi-file torrent Infos

metainfo/metainfo.go

@@ -46,6 +46,10 @@ type Info struct {
 	Files       []FileInfo `bencode:"files,omitempty"`
 }
 
+func (i *Info) IsDir() bool {
+	return len(i.Files) != 0
+}
+
 // The files field, converted up from the old single-file in the parent info
 // dict if necessary. This is a helper to avoid having to conditionally handle
 // single and multi-file torrent infos.
@@ -53,7 +57,9 @@ func (i *Info) UpvertedFiles() []FileInfo {
 	if len(i.Files) == 0 {
 		return []FileInfo{{
 			Length: i.Length,
-			Path:   []string{i.Name},
+			// Callers should determine that Info.Name is the basename, and
+			// thus a regular file.
+			Path: nil,
 		}}
 	}
 	return i.Files