Re: [PATCH 7/7] ci: run test round with parallel-checkout enabled

> We already have tests for the basic parallel-checkout operations. But
> this code can also run be executed by other commands, such as
> git-read-tree and git-sparse-checkout, which are currently not tested
> with multiple workers. To promote a wider test coverage without
> duplicating tests:
> 
> 1. Add the GIT_TEST_CHECKOUT_WORKERS environment variable, to optionally
>    force parallel-checkout execution during the whole test suite.
> 
> 2. Set this variable (with a value of 2) in the second test round of our
>    linux-gcc CI job. This round runs `make test` again with some
>    optional GIT_TEST_* variables enabled, so there is no additional
>    overhead in exercising the parallel-checkout code here.
> 
> Note that tests checking out less than two parallel-eligible entries
> will fall back to the sequential mode. Nevertheless, it's still a good
> exercise for the parallel-checkout framework as the fallback codepath
> also writes the queued entries using the parallel-checkout functions
> (only without spawning any worker).

> Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
> ---
>  ci/run-build-and-tests.sh  |  1 +
>  parallel-checkout.c        | 14 ++++++++++++++
>  t/README                   |  4 ++++
>  t/lib-parallel-checkout.sh |  3 +++
>  4 files changed, 22 insertions(+)
> 
> diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
> index a66b5e8c75..23b28e7391 100755
> --- a/ci/run-build-and-tests.sh
> +++ b/ci/run-build-and-tests.sh
> @@ -25,6 +25,7 @@ linux-gcc)
>  	export GIT_TEST_ADD_I_USE_BUILTIN=1
>  	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master
>  	export GIT_TEST_WRITE_REV_INDEX=1
> +	export GIT_TEST_CHECKOUT_WORKERS=2
>  	make test
>  	;;

>  void get_parallel_checkout_configs(int *num_workers, int *threshold)
>  {
> +	char *env_workers = getenv("GIT_TEST_CHECKOUT_WORKERS");
> +
> +	if (env_workers && *env_workers) {
> +		if (strtol_i(env_workers, 10, num_workers)) {

> +			die("invalid value for GIT_TEST_CHECKOUT_WORKERS: '%s'",
> +			    env_workers);
> +		}
> +		if (*num_workers < 1)
> +			*num_workers = online_cpus();
> +
> +		*threshold = 0;
> +		return;
> +	}