Merge pull request #32670 from perweij/fix-Dockerfile-instruction

Correcting test-instruction.

Dockerfile

@@ -9,7 +9,7 @@
 # docker run -v `pwd`:/go/src/github.com/docker/docker --privileged -i -t docker bash
 #
 # # Run the test suite:
-# docker run --privileged docker hack/make.sh test-unit test-integration-cli test-docker-py
+# docker run -e DOCKER_GITCOMMIT=foo --privileged docker hack/make.sh test-unit test-integration-cli test-docker-py
 #
 # # Publish a release:
 # docker run --privileged \