Re: [PATCH 1/2] t/perf: fix regression in testing older versions of git

> Commit 7501b59 (perf: make the tests work in worktrees,
> 2016-05-13) introduced the use of "git rev-parse --git-path"
> in the perf-lib setup code. Because the to-be-tested version
> of git is at the front of the $PATH when this code runs,
> this means we cannot use modern versions of t/perf to test
> versions of git older than v2.5.0 (when that option was
> introduced).
> 
> This is a symptom of a more general problem. The t/perf
> suite is essentially independent of git versions, and
> ideally we would be able to run the most modern and complete
> set of tests across many historical versions (to see how
> they compare). But any setup code they run is therefore
> required to use the lowest common denominator we expect to
> test.
> 
> So let's introduce a new variable, $MODERN_GIT, that we can
> use both in perf-lib and in the test setup to get a reliable
> set of git features (we might change git and break some
> tests, of course, but $MODERN_GIT is tied to the same
> version of git as the t/perf scripts, so they can be fixed
> or adjusted together).
> 
> This commit fixes the "--git-path" case, but does not
> mass-convert existing setup code to use $MODERN_GIT. Most
> setup code is fairly vanilla and will work with effectively
> all versions. But now the tool is there to fix any other
> issues we find going forward.