commit: minor fix on bug cut

commit.go

@@ -85,9 +85,7 @@ func (c *Commit) IsImageFile(name string) bool {
 	}
 	buf := make([]byte, 1024)
 	n, _ := dataRc.Read(buf)
-	if n > 0 {
-		buf = buf[:n]
-	}
+	buf = buf[:n]
 	_, isImage := isImageFile(buf)
 	return isImage
 }