Re: [PATCH 2/3] t7900: exercise detaching via trace2 regions

> In t7900, we exercise the `--detach` logic by checking whether the
> command ended up writing anything to its output or not. This supposedly
> works because we close stdin, stdout and stderr when daemonizing. But
> one, it breaks on platforms where daemonize is a no-op, like Windows.
> And second, that git-maintenance(1) outputs anything at all in these
> tests is a bug in the first place that we'll fix in a subsequent commit.
> 
> Introduce a new trace2 region around the detach which allows us to more
> explicitly check whether the detaching logic was executed. This is a
> much more direct way to exercise the logic, provides a potentially
> useful signal to tracing logs and also works alright on platforms which
> do not have the ability to daemonize.

> diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
> index 074eadcd1c..46a61d66fb 100755
> --- a/t/t7900-maintenance.sh
> +++ b/t/t7900-maintenance.sh
> @@ -950,8 +950,9 @@ test_expect_success '--no-detach causes maintenance to not run in background' '
>  		# We have no better way to check whether or not the task ran in
>  		# the background than to verify whether it output anything. The
>  		# next testcase checks the reverse, making this somewhat safer.
> -		git maintenance run --no-detach >out 2>&1 &&
> -		test_line_count = 1 out
> +		GIT_TRACE2_EVENT="$(pwd)/trace.txt" \
> +			git maintenance run --no-detach >out 2>&1 &&
> +		! test_region maintenance detach trace.txt
>  	)
>  '