Switch template.config to TOFS pattern

pillar.example

@@ -1,3 +1,10 @@
 template:
   lookup:
     master: template-master
+
+  # The files_switch key serves as a selector for alternative
+  # directories under the formula files directory. See TOFS pattern
+  # doc for more info.
+  files_switch:
+    - id
+    - os_familly

template/config.sls

@@ -2,11 +2,12 @@
 # vim: ft=sls
 
 {% from "template/map.jinja" import template with context %}
+{% from "template/macros.jinja" import files_switch with context %}
 
 template-config:
   file.managed:
     - name: {{ template.config }}
-    - source: salt://template/files/example.tmpl
+    - source: {{ files_switch('template', ['example.tmpl'] }}
     - mode: 644
     - user: root
     - group: root

template/files/default/example.tmpl

@@ -0,0 +1,3 @@
+# Managed by saltstack
+
+This is an example file from SaltStack template-formula.