stage1: better file path handling

* better message printed when cache hash fails
 * better handling of '/' as root source file
 * os_path_split parses '/' and '/a' correctly

closes #1693
closes #1746
67a39a4c99Andrew Kelley committed on 11/27/2018, 1:04:35 AMparentd2ed4d3
5 files changedLine totals unavailable