[PATCH 0/2] t/perf tests against older versions

One of the points of the t/perf suite is to be able to detect
performance regressions between versions. But I don't think anybody
really runs it systematically; we mostly just use it to show off our
shiny new improvements. :)

So I decided to run the suite against v2.0.0 and v2.9.0, to catch any
regressions that have crept in the past few years. The good news is that
there aren't any. But I did need a few patches to show that:

  [1/2]: t/perf: fix regression in testing older versions of git
  [2/2]: p4211: explicitly disable renames in no-rename test

The first one fixes the issue I reported in [1], which let me run the
suite against v2.0.0 at all. And the second fixes something that looks
like a regression in the results, but really isn't.

-Peff

[1] http://article.gmane.org/gmane.comp.version-control.git/297875