p3400: add perf tests for rebasing many changes

Rebasing onto many changes is interesting, but it's also
interesting to see what happens when rebasing many changes.

And while at it, let's also look at the impact of using a
split index.
Signed-off-by: NChristian Couder <chriscool@tuxfamily.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/perf/p3400-rebase.sh

@@ -5,7 +5,7 @@ test_description='Tests rebase performance'
 
 test_perf_default_repo
 
-test_expect_success 'setup' '
+test_expect_success 'setup rebasing on top of a lot of changes' '
 	git checkout -f -b base &&
 	git checkout -b to-rebase &&
 	git checkout -b upstream &&
@@ -33,4 +33,24 @@ test_perf 'rebase on top of a lot of unrelated changes' '
 	git rebase --onto base HEAD^
 '
 
+test_expect_success 'setup rebasing many changes without split-index' '
+	git config core.splitIndex false &&
+	git checkout -b upstream2 to-rebase &&
+	git checkout -b to-rebase2 upstream
+'
+
+test_perf 'rebase a lot of unrelated changes without split-index' '
+	git rebase --onto upstream2 base &&
+	git rebase --onto base upstream2
+'
+
+test_expect_success 'setup rebasing many changes with split-index' '
+	git config core.splitIndex true
+'
+
+test_perf 'rebase a lot of unrelated changes with split-index' '
+	git rebase --onto upstream2 base &&
+	git rebase --onto base upstream2
+'
+
 test_done