Feature: Flag/ENV to turn off regression comparisons

[peter-lyons-kehl]

Please add a flag/env variable to turn off regression. Useful with compare_by_id when we only want to compare performance of various implementations, especially if the behavior varies: depending on input files, randomness... - then regression is misleading.

[gamma0987]

What exactly do you mean with regression?

[gamma0987]

Sorry, that it took some time. In v0.17.0, I've added a command-line argument --show-only-comparison and an env var GUNGRAUN_SHOW_ONLY_COMPARISON. This option suppresses the usual self comparisons between the old and new run and only comparisons with other benchmarks are shown. I hope this is is what you wanted.