Merge branch 'ds/ci-commit-graph-and-midx'

One of our CI tests to run with "unusual/experimental/random"
settings now also uses commit-graph and midx.

* ds/ci-commit-graph-and-midx:
  ci: add optional test variables

Author: gitster

ci/run-build-and-tests.sh

@@ -15,6 +15,8 @@ then
 	export GIT_TEST_FULL_IN_PACK_ARRAY=true
 	export GIT_TEST_OE_SIZE=10
 	export GIT_TEST_OE_DELTA_SIZE=5
+	export GIT_TEST_COMMIT_GRAPH=1
+	export GIT_TEST_MULTI_PACK_INDEX=1
 	make --quiet test
 fi