Add multi-module check to prow-presubmit-check

Makefile

@@ -6,6 +6,7 @@
 MYGOBIN := $(shell go env GOPATH)/bin
 SHELL := /bin/bash
 export PATH := $(MYGOBIN):$(PATH)
+MODULES := "cmd/config" "api/" "kustomize/" "kyaml/"
 
 .PHONY: all
 all: verify-kustomize
@@ -24,6 +25,7 @@ verify-kustomize: \
 # https://github.com/kubernetes/test-infra/tree/master/config/jobs/kubernetes-sigs/kustomize
 .PHONY: prow-presubmit-check
 prow-presubmit-check: \
+	test-multi-module \
 	lint-kustomize \
 	test-unit-kustomize-all \
 	test-examples-kustomize-against-HEAD \
@@ -220,6 +222,17 @@ test-unit-cmd-all:
 test-go-mod:
 	./travis/check-go-mod.sh
 
+# Environment variables are defined at
+# https://github.com/kubernetes/test-infra/blob/master/prow/jobs.md#job-environment-variables
+.PHONY: test-multi-module
+test-multi-module:
+	go install github.com/google/go-github/github
+	go run ./travis/module-span/multi-module-span.go \
+	-owner=$(REPO_OWNER) \
+	-repo=$(REPO_NAME) \
+	-pr=$(PR_NUM) \
+	$(MODULES)
+
 .PHONY:
 test-examples-e2e-kustomize: $(MYGOBIN)/mdrip $(MYGOBIN)/kind
 	( \

travis/module-span/multi-module-span.go

@@ -57,15 +57,30 @@ func main() {
 // ListAllPullRequestFiles retrieves as many files as possible for the
 // target pull request.
 //
-// NOTE: GitHub API limits ListFiles to a maximum of 3000 files. Very large
+// Note: GitHub API limits ListFiles to a maximum of 3000 files. Very large
 // changes which exceed this limit may pass this check even if they
 // do contain spanning changes.
 // see: https://developer.github.com/v3/pulls/#list-pull-requests-files
 func ListAllPullRequestFiles(client *github.Client, owner *string, pullrequest *int, repo *string) ([]*github.CommitFile, error) {
+	// foundFiles across all pages from github api
+	var foundFiles []*github.CommitFile
 	// GitHub returns the first 30 files by default, increase this value
-	options := &github.ListOptions{PerPage: 3000}
-	files, _, err := client.PullRequests.ListFiles(context.Background(), *owner, *repo, *pullrequest, options)
-	return files, err
+	// Note: Page 1 is the first page of results. Page 0 is an end of list mark.
+	// Github only returns (max) 100 results per page and PR's may exceed this
+	// so loop until all pages have been enumerated.
+	options := &github.ListOptions{PerPage: 100, Page: 1}
+	for options.Page != 0 {
+		files, response, err := client.PullRequests.ListFiles(context.Background(), *owner, *repo, *pullrequest, options)
+
+		// If an error has occurred while querying api exit early, report error
+		if err != nil {
+			return nil, err
+		}
+		foundFiles = append(foundFiles, files...)
+		// setup next page to continue loop
+		options = &github.ListOptions{PerPage: 100, Page: response.NextPage}
+	}
+	return foundFiles, nil
 }
 
 // CountModifiedRestrictedDirectories Accepts a map of paths and the number of