Re: [PATCH] t/perf/run: fix bin-wrappers computation

[Derrick Stolee <stolee@gmail.com>]

On 9/21/2021 1:50 PM, Taylor Blau wrote:
> On Tue, Sep 21, 2021 at 03:46:12PM +0000, Derrick Stolee via GitGitGadget wrote:
>> This is critical to successfully computing performance of commands that
>> execute subcommands. The bin-wrappers ensure that the --exec-path is set
>> correctly.
> 
> Just sanity-checking everything you said: with this bug, we'll set
> mydir_abs_wrappers to "/bin-wrappers", then realize that directory
> doesn't exist, and fall back to GIT_TEST_INSTALLED=$mydir_abs. Putting
> 'set -x' at the top of t/perf/run, we can see the relevant section:
> 
>   + mydir=build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + cd build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + pwd
>   + mydir_abs=/home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + mydir_abs_wrappers=/bin-wrappers
>   + test -d /bin-wrappers
>   + GIT_TEST_INSTALLED=/home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
>   + export GIT_TEST_INSTALLED
> 
> OK. But the real problem is in t/test-lib.sh where we read
> "$GIT_TEST_INSTALLED". There we ask for the `--exec-path`, which appears
> to be wrong, at least in my setup. Printing out the $GIT_EXEC_PATH and
> $GIT_TEST_INSTALLED, I get:
> 
>   /home/ttaylorr/local/git/ds.sparse-checkout/libexec/git-core,
>   /home/ttaylorr/src/git/t/perf/build/73cd7d9420bb7d75207e8149521db375c789a81c
> 
> where the former is the branch I happen to have checked out, and the
> latter is the revision that I asked to run performance tests on via
> t/perf/run.
> 
> So I think we'll run the right top-level Git command since the latter
> path ends up first in our $PATH, but the exec path is definitely wrong.

Thanks for digging into this more. This issue with GIT_EXEC_PATH explains
some strangeness I was seeing.

Perhaps there is something more robust to be done around GIT_EXEC_PATH,
but the current fix satisfies my needs.
 
>> diff --git a/t/perf/run b/t/perf/run
>> index d19dec258a2..55219aa4056 100755
>> --- a/t/perf/run
>> +++ b/t/perf/run
>> @@ -74,7 +74,7 @@ set_git_test_installed () {
>>  	mydir=$1
>>
>>  	mydir_abs=$(cd $mydir && pwd)
>> -	mydir_abs_wrappers="$mydir_abs_wrappers/bin-wrappers"
>> +	mydir_abs_wrappers="$mydir_abs/bin-wrappers"
> 
> This fix looks obviously right to me (and gives me the expected output
> from above when I apply it locally).

Thanks,
-Stolee