The github differencing logic is piecing stuff from high and low.  The real change is that I inserted "if (RunningCompactionCount()<2)", then tabbed everything else in the function in by one tab.  Old (red) line 248 is now new (green) line 256.  Move 7 lines down in red, then in green ... both have same "KeepOrDelete(filenames[i], -1, live)".  Move 19 lines down from the starting point.  You will see "KeepOrDelete(filenames[i], level, live);" in both.