out.Flush()
				base.Fatalf("%s", err)
			}
			out.Write(b)
			out.Write(nl)
		}
	} else {
		var cachedCtxt *Context
		context := func() *Context {
			if cachedCtxt == nil {
				cachedCtxt = newContext(&cfg.BuildContext)
			}
			return cachedCtxt
		}
		fm := template.FuncMap{
			"join":    strings.Join,
			"context": context,