Merge branch 'ds/commit-graph-tests'

We can now optionally run tests with commit-graph enabled. * ds/commit-graph-tests: commit-graph: define GIT_TEST_COMMIT_GRAPH

Junio C Hamano committed Sep 17, 2018 at 13:53 UTC 06880cff3892185ae71839636e2d2c688413eccb

No changes.