Move flagbuilder to a shared package

Splitting up the CoreOS PR into manageable chunks

hack/.packages

@@ -28,6 +28,7 @@ k8s.io/kops/pkg/client/simple
 k8s.io/kops/pkg/client/simple/vfsclientset
 k8s.io/kops/pkg/diff
 k8s.io/kops/pkg/featureflag
+k8s.io/kops/pkg/flagbuilder
 k8s.io/kops/pkg/kubeconfig
 k8s.io/kops/pkg/model
 k8s.io/kops/pkg/model/components

pkg/flagbuilder/build_flags.go

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package nodeup
+package flagbuilder
 
 import (
 	"fmt"
@@ -25,8 +25,8 @@ import (
 	"strings"
 )
 
-// buildFlags is a template helper, which builds a string containing the flags to be passed to a command
-func buildFlags(options interface{}) (string, error) {
+// BuildFlags builds flag arguments based on "flag" tags on the structure
+func BuildFlags(options interface{}) (string, error) {
 	var flags []string
 
 	walker := func(path string, field *reflect.StructField, val reflect.Value) error {

upup/pkg/fi/nodeup/template_functions.go

@@ -26,6 +26,7 @@ import (
 	"github.com/golang/glog"
 	"k8s.io/kops"
 	api "k8s.io/kops/pkg/apis/kops"
+	"k8s.io/kops/pkg/flagbuilder"
 	"k8s.io/kops/upup/pkg/fi"
 	"k8s.io/kops/upup/pkg/fi/secrets"
 	"k8s.io/kops/util/pkg/vfs"
@@ -123,7 +124,7 @@ func (t *templateFunctions) populate(dest template.FuncMap) {
 	dest["AllTokens"] = t.AllTokens
 	dest["GetToken"] = t.GetToken
 
-	dest["BuildFlags"] = buildFlags
+	dest["BuildFlags"] = flagbuilder.BuildFlags
 	dest["Base64Encode"] = func(s string) string {
 		return base64.StdEncoding.EncodeToString([]byte(s))
 	}