Unify command line namespace resolution

This change allows the namespace in kubeconfig to be overridden by
specifying the namespace in the spec file. If namespace is explicitly
provided in the command line flags and the spec file has a different
namespace, this will cause an error.

pkg/kubectl/resource/builder.go

@@ -87,9 +87,12 @@ func (b *Builder) Schema(schema validation.Schema) *Builder {
 }
 
 // FilenameParam groups input in two categories: URLs and files (files, directories, STDIN)
+// If enforceNamespace is false, namespaces in the specs will be allowed to
+// override the default namespace. If it is true, namespaces that don't match
+// will cause an error.
 // If ContinueOnError() is set prior to this method, objects on the path that are not
 // recognized will be ignored (but logged at V(2)).
-func (b *Builder) FilenameParam(paths ...string) *Builder {
+func (b *Builder) FilenameParam(enforceNamespace bool, paths ...string) *Builder {
 	for _, s := range paths {
 		switch {
 		case s == "-":
@@ -105,6 +108,11 @@ func (b *Builder) FilenameParam(paths ...string) *Builder {
 			b.Path(s)
 		}
 	}
+
+	if enforceNamespace {
+		b.RequireNamespace()
+	}
+
 	return b
 }