This patch cleans up a number of issues with how compare_bench.py handled
the command line arguments.
* Use the 'argparse' python module instead of hand rolled parsing. This gives
better usage messages.
* Add diagnostics for certain --benchmark flags that cannot or should not
be used with compare_bench.py (eg --benchmark_out_format=csv).
* Don't override the user specified --benchmark_out flag if it's provided.
In future I would like the user to be able to capture both benchmark output
files, but this change is big enough for now.
This fixes issue #313.
This patch adds the compare_bench.py utility which can be used to compare the result of benchmarks.
The program is invoked like:
$ compare_bench.py <old-benchmark> <new-benchmark> [benchmark options]...
Where <old-benchmark> and <new-benchmark> either specify a benchmark executable file, or a JSON output file. The type of the input file is automatically detected. If a benchmark executable is specified then the benchmark is run to obtain the results. Otherwise the results are simply loaded from the output file.
