p0071: measure sorting of already sorted and reversed files

Check if sorting takes advantage of already sorted or reversed content,
or if that corner case actually decreases performance, like it would for
a simplistic quicksort implementation.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/perf/p0071-sort.sh

@@ -11,16 +11,31 @@ test_expect_success 'setup' '
 	git cat-file --batch >unsorted
 '
 
-test_perf 'sort(1)' '
+test_perf 'sort(1) unsorted' '
-	sort <unsorted >expect
+	sort <unsorted >sorted
 '
 
-test_perf 'string_list_sort()' '
+test_expect_success 'reverse' '
-	test-tool string-list sort <unsorted >actual
+	sort -r <unsorted >reversed
 '
 
-test_expect_success 'string_list_sort() sorts like sort(1)' '
+for file in sorted reversed
-	test_cmp_bin expect actual
+do
-'
+	test_perf "sort(1) $file" "
+		sort <$file >actual
+	"
+done
+
+for file in unsorted sorted reversed
+do
+
+	test_perf "string_list_sort() $file" "
+		test-tool string-list sort <$file >actual
+	"
+
+	test_expect_success "string_list_sort() $file sorts like sort(1)" "
+		test_cmp_bin sorted actual
+	"
+done
 
 test_done