erp5: Use erp5-doc as external repository

stack/erp5/buildout.cfg

@@ -348,6 +348,11 @@ link-binary =
 repository = https://lab.nexedi.com/nexedi/erp5-bin.git
 branch = master
 
+[erp5-doc]
+<= erp5
+repository = https://lab.nexedi.com/nexedi/erp5-doc.git
+branch = master
+
 [bt5-repository]
 # Format:
 #   <url or path> [...]
@@ -359,7 +364,7 @@ list = ${local-bt5-repository:list}
 [local-bt5-repository]
 # Same as bt5-repository, but only local repository.
 # Used to generate bt5lists.
-list = ${erp5:location}/bt5 ${erp5:location}/product/ERP5/bootstrap ${erp5-bin:location}/bt5
+list = ${erp5:location}/bt5 ${erp5:location}/product/ERP5/bootstrap ${erp5-bin:location}/bt5 ${erp5-doc:location}
 
 [genbt5list]
 recipe = plone.recipe.command
@@ -370,7 +375,7 @@ command =
 update-command = ${:command}
 
 [erp5_repository_list]
-repository_id_list = erp5 erp5-bin
+repository_id_list = erp5 erp5-bin erp5-doc
 
 # ERP5 defaults, which can be overridden in inheriting recipes (e.g. wendelin)
 [erp5-defaults]