Add conformance test commands to Makefile

Signed-off-by: Cody Soyland <codysoyland@github.com>

.gitignore

@@ -30,5 +30,7 @@ cosignImagerefs
 bundle
 signature
 certificate
+sigstore-conformance
+conformance
 
 **verify-experimental*

CONTRIBUTING.md

@@ -41,6 +41,21 @@ make test
 
 **Make sure all tests pass** without any failures or errors.
 
+#### Conformance tests
+
+To run the conformance tests, first install the conformance test runner:
+
+```shell
+make conformance-runner
+```
+
+Then build `cosign` and `conformance` (the executable that adapts conformance tests to the cosign command), and run the tests:
+
+```shell
+make cosign conformance
+make conformance-tests
+```
+
 ### Running Lint
 
 To run the linting checks, use the following command:

Makefile

@@ -112,9 +112,6 @@ lint: golangci-lint ## Run golangci-lint linter
 test:
 	$(GOEXE) test $(shell $(GOEXE) list ./... | grep -v third_party/)
 
-conformance:
-	$(GOEXE) build -trimpath -ldflags "$(LDFLAGS)" -o $@ ./cmd/conformance
-
 clean:
 	rm -rf cosign
 	rm -rf dist/
@@ -133,6 +130,34 @@ define create_kocache_path
   mkdir -p $(KOCACHE_PATH)
 endef
 
+###################
+# conformance tests
+###################
+
+conformance:
+	$(GOEXE) build -trimpath -ldflags "$(LDFLAGS)" -o $@ ./cmd/conformance
+
+CONFORMANCE_RUNNER_PATH = sigstore-conformance
+$(CONFORMANCE_RUNNER_PATH):
+	git clone https://github.com/sigstore/sigstore-conformance $@
+
+.PHONY: conformance-runner
+conformance-runner:
+	$(MAKE) $(CONFORMANCE_RUNNER_PATH) conformance-runner-pull conformance-runner-build
+
+.PHONY: conformance-runner-pull
+conformance-runner-pull:
+	cd $(CONFORMANCE_RUNNER_PATH) && git pull
+
+.PHONY: conformance-runner-build
+conformance-runner-build:
+	cd $(CONFORMANCE_RUNNER_PATH) && $(MAKE) dev
+
+CONFORMANCE_BIN = $(shell pwd)/conformance
+.PHONY: conformance-tests
+conformance-tests:
+	cd $(CONFORMANCE_RUNNER_PATH) && env/bin/pytest test --entrypoint=$(CONFORMANCE_BIN)
+
 ##########
 # ko build
 ##########