t/perf: factor boilerplate out of test_perf

About half of test_perf() is boilerplate preparing to run
_any_ test, and the other half is specifically running a
timing test. Let's split it into two functions, so that we
can reuse the boilerplate in future commits.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/perf/perf-lib.sh

@@ -179,8 +179,8 @@ exit $ret' >&3 2>&4
 	return "$eval_ret"
 }
 
-
-test_perf () {
+test_wrapper_ () {
+	test_wrapper_func_=$1; shift
 	test_start_
 	test "$#" = 3 && { test_prereq=$1; shift; } || test_prereq=
 	test "$#" = 2 ||
@@ -191,6 +191,14 @@ test_perf () {
 		base=$(basename "$0" .sh)
 		echo "$test_count" >>"$perf_results_dir"/$base.subtests
 		echo "$1" >"$perf_results_dir"/$base.$test_count.descr
+		base="$perf_results_dir"/"$perf_results_prefix$(basename "$0" .sh)"."$test_count"
+		"$test_wrapper_func_" "$@"
+	fi
+
+	test_finish_
+}
+
+test_perf_ () {
 	if test -z "$verbose"; then
 		printf "%s" "perf $test_count - $1:"
 	else
@@ -216,10 +224,11 @@ test_perf () {
 	else
 		test_ok_ "$1"
 	fi
-		base="$perf_results_dir"/"$perf_results_prefix$(basename "$0" .sh)"."$test_count"
 	"$TEST_DIRECTORY"/perf/min_time.perl test_time.* >"$base".times
-	fi
-	test_finish_
+}
+
+test_perf () {
+	test_wrapper_ test_perf_ "$@"
 }
 
 # We extend test_done to print timings at the end (./run disables this