Allow control over dirs passed to e2e and unit tests

Allows e.g.:

    $ make -f docker.Makefile TESTDIRS=./cli/command/trust/... test-unit

Signed-off-by: Ian Campbell <ijc@docker.com>

Makefile

@@ -12,7 +12,7 @@ clean: ## remove build artifacts
 
 .PHONY: test-unit
 test-unit: ## run unit tests, to change the output format use: GOTESTSUM_FORMAT=(dots|short|standard-quiet|short-verbose|standard-verbose) make test-unit 
-	gotestsum $(TESTFLAGS) -- $(shell go list ./... | grep -vE '/vendor/|/e2e/')
+	gotestsum $(TESTFLAGS) -- $${TESTDIRS:-$(shell go list ./... | grep -vE '/vendor/|/e2e/')}
 
 .PHONY: test
 test: test-unit ## run tests

docker.Makefile

@@ -21,7 +21,7 @@ ifeq ($(DOCKER_CLI_GO_BUILD_CACHE),y)
 DOCKER_CLI_MOUNTS += -v "$(CACHE_VOLUME_NAME):/root/.cache/go-build"
 endif
 VERSION = $(shell cat VERSION)
-ENVVARS = -e VERSION=$(VERSION) -e GITCOMMIT -e PLATFORM -e TESTFLAGS
+ENVVARS = -e VERSION=$(VERSION) -e GITCOMMIT -e PLATFORM -e TESTFLAGS -e TESTDIRS
 
 # build docker image (dockerfiles/Dockerfile.build)
 .PHONY: build_docker_image

scripts/test/e2e/run

@@ -70,7 +70,7 @@ function runtests {
         GOPATH="$GOPATH" \
         PATH="$PWD/build/:/usr/bin:/usr/local/bin:/usr/local/go/bin" \
         DOCKER_CLI_E2E_PLUGINS_EXTRA_DIRS="$PWD/build/plugins-linux-amd64" \
-        "$(command -v gotestsum)" -- ./e2e/... ${TESTFLAGS-}
+        "$(command -v gotestsum)" -- ${TESTDIRS:-./e2e/...} ${TESTFLAGS-}
 }
 
 export unique_id="${E2E_UNIQUE_ID:-cliendtoendsuite}"