contrib/asv.conf.json

perf: allow to clear the obsstore in 'perfvolatilesets'

Loading the obsstore can become a large part of the time necessary to compute
the important volatile set. We add a flag purging all known obsstore related
data.

For example, computing the 'bumped' set currently requires reading the full
obsstore, so timing greatly differ with or without that flag:

Without:
! bumped
! wall 0.005047 comb 0.000000 user 0.000000 sys 0.000000 (best of 446)

With:
! bumped
! wall 0.512367 comb 0.510000 user 0.480000 sys 0.030000 (best of 15)

{
    "version": 1,
    "project": "mercurial",
    "project_url": "https://mercurial-scm.org/",
    "repo": "..",
    "branches": ["default", "stable"],
    "environment_type": "virtualenv",
    "show_commit_url": "https://www.mercurial-scm.org/repo/hg/rev/",
    "benchmark_dir": "benchmarks",
    "env_dir": "../.asv/env",
    "results_dir": "../.asv/results",
    "html_dir": "../.asv/html"
}