add go-apidiff to verify api differences

- create apidiff.yaml in github workflows
- Added `apidiff` target to Makefile for local testing
- Always compare with master for any api differences
- Invoke tests in CI only on pull_request from a different repo

.github/workflows/apidiff.yml

@@ -0,0 +1,36 @@
+name: APIDiff
+
+# Trigger the workflow on pull requests and direct pushes to any branch
+on:
+  push:
+  pull_request:
+
+jobs:
+  go-apidiff:
+    name: Verify API differences
+    runs-on: ubuntu-latest
+    # Pull requests from different repository only trigger this checks
+    if: github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository
+    steps:
+      - name: Clone the code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Setup Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: '1.15'
+      - name: Execute go-apidiff
+        uses: joelanford/[email protected]
+        with:
+          compare-imports: true
+          print-compatible: true
+      - name: Report failure
+        uses: nashmaniac/[email protected]
+        # Only report failures of pushes (PRs have are visible through the Checks section) to the default branch
+        if: failure() && github.event_name == 'push' && github.ref == 'refs/heads/master'
+        with:
+          title: 🐛 go-apidiff failed for ${{ github.sha }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+          labels: kind/bug
+          body: https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}

Makefile

@@ -85,6 +85,16 @@ golangci-lint:
 	curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(shell dirname $(GOLANGCI_LINT)) v1.37.1 ;\
 	}
 
+.PHONY: apidiff
+apidiff: go-apidiff ## Run the go-apidiff to verify any API differences compared with origin/master
+	$(GO_APIDIFF) master --compare-imports --print-compatible --repo-path=.
+
+GO_APIDIFF = $(shell pwd)/bin/go-apidiff
+go-apidiff:
+	@[ -f $(GO_APIDIFF) ] || { \
+	cd tools && go build -tags=tools -o $(GO_APIDIFF) github.com/joelanford/go-apidiff ;\
+	}
+
 ##@ Tests
 
 .PHONY: test

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/cloudflare/cfssl v1.5.0 // for `kubebuilder alpha config-gen`
 	github.com/go-logr/logr v0.3.0 // indirect
 	github.com/gobuffalo/flect v0.2.2
+	github.com/joelanford/go-apidiff v0.1.0
 	// TODO: remove this in favor of embed once using 1.16
 	github.com/markbates/pkger v0.17.1 // for `kubebuilder alpha config-gen`
 	github.com/onsi/ginkgo v1.15.0