src/Pure/Admin/build_log.scala
2016-10-13 wenzelm 2016-10-13 more robust wrt. old versions that use clear-text properties (e.g. Timing in build_history_base);
2016-10-13 wenzelm 2016-10-13 clarified log_subdir vs. log_filename; support for sequential and parallel task blocks (unnamed);
2016-10-12 wenzelm 2016-10-12 clarified files;