feat: add dockerignore file to the scaffold (V3 only)

docs/book/src/cronjob-tutorial/testdata/project/.dockerignore

@@ -0,0 +1,5 @@
+# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore all files which are not go type
+!**/*.go
+!**/*.mod
+!**/*.sum

docs/book/src/multiversion-tutorial/testdata/project/.dockerignore

@@ -0,0 +1,5 @@
+# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore all files which are not go type
+!**/*.go
+!**/*.mod
+!**/*.sum

pkg/plugin/v3/scaffolds/init.go

@@ -112,6 +112,7 @@ func (s *initScaffolder) scaffold() error {
 			KustomizeVersion:       KustomizeVersion,
 		},
 		&templates.Dockerfile{},
+		&templates.DockerignoreFile{},
 		&templates.Kustomize{},
 		&templates.ManagerWebhookPatch{},
 		&templates.ManagerRoleBinding{},

pkg/plugin/v3/scaffolds/internal/templates/dockerignorefile.go

@@ -0,0 +1,46 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package templates
+
+import (
+	"sigs.k8s.io/kubebuilder/pkg/model/file"
+)
+
+var _ file.Template = &DockerignoreFile{}
+
+// Dockerfile scaffolds a DockerignoreFile for building a main
+type DockerignoreFile struct {
+	file.TemplateMixin
+}
+
+// SetTemplateDefaults implements input.Template
+func (f *DockerignoreFile) SetTemplateDefaults() error {
+	if f.Path == "" {
+		f.Path = ".dockerignore"
+	}
+
+	f.TemplateBody = dockerignorefileTemplate
+
+	return nil
+}
+
+const dockerignorefileTemplate = `# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore all files which are not go type
+!**/*.go
+!**/*.mod
+!**/*.sum
+`

testdata/project-v3-addon/.dockerignore

@@ -0,0 +1,5 @@
+# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore all files which are not go type
+!**/*.go
+!**/*.mod
+!**/*.sum

testdata/project-v3-multigroup/.dockerignore

@@ -0,0 +1,5 @@
+# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore all files which are not go type
+!**/*.go
+!**/*.mod
+!**/*.sum

testdata/project-v3/.dockerignore

@@ -0,0 +1,5 @@
+# More info: https://docs.docker.com/engine/reference/builder/#dockerignore-file
+# Ignore all files which are not go type
+!**/*.go
+!**/*.mod
+!**/*.sum