[DOC] document singleton behaviour in type manpage

Signed-off-by: Nico Schottelius <nico@kr.ethz.ch>

bin/cdist-config

@@ -19,7 +19,7 @@
 #
 #
 
-# Fail if something bogus is going on and export all variables
+# Fail if something bogus is going on
 set -u
 
 ################################################################################

doc/dev/todo/niconext

@@ -1,7 +1,11 @@
-- Support singletons (see types/issue for a good reason)
-   - add documentation!
-
 - think about splitting __file:
-   __file --source
-   __directory --recursive yes|no --source
-   __link --type symbolic|hard
+   __file 
+      source
+      mode
+      owner
+   __directory
+      parents
+      mode
+      owner
+   __link 
+      type symbolic | hard

doc/man/cdist-type.text

@@ -10,7 +10,9 @@ cdist-type - Functionality bundled
 
 SYNOPSIS
 --------
-Other languages name this module or class 
+__TYPE ID --parameter value [--parameter value ...]
+
+__TYPE --parameter value [--parameter value ...] (for singletons)
 
 
 DESCRIPTION
@@ -37,7 +39,23 @@ Internally cdist-type-emulator(1) will be called from cdist-manifest-run(1) to
 save the given parameters into a cconfig database, so they can be accessed by
 the manifest and gencode scripts of the type (see below).
 
-A list of supported types can be found in the cdist-type-listing(7) manpage.
+A list of supported types can be found in the cdist-reference(7) manpage.
+
+SINGLETON TYPES
+---------------
+If a type is flagged as a singleton, it may me used only once. This
+is useful for types which can be used only once on a system. If a type
+can only be used once, it does not take an 
+
+Example:
+--------------------------------------------------------------------------------
+# __issue type manages /etc/issue
+__issue
+
+# Probably your own type - singletons may use parameters
+__myfancysingleton --colour green
+--------------------------------------------------------------------------------
+
 
 
 HOW TO WRITE A NEW TYPE
@@ -46,6 +64,7 @@ A type consists of
 
 - parameter (optional)
 - manifest  (optional)
+- singleton (optional)
 - explorer  (optional)
 - gencode   (optional)
 
@@ -98,6 +117,20 @@ Always ensure the manifest is executable, otherwise cdist will not be able
 to execute it.
 
 
+SINGLETON - ONLY INSTANCE ONLY
+------------------------------
+If you want to ensure that a type can only be used once per target, you can
+mark it as a singleton: Just create the (empty) file "singleton" in your type
+directory. This will also change the way your type must be called:
+
+--------------------------------------------------------------------------------
+__YOURTYPE --parameter value
+--------------------------------------------------------------------------------
+
+As you can see, the ID is omitted, because it does not make any sense, if your
+type can be used only once.
+
+
 THE TYPE EXPLORERS
 ------------------
 If a type needs to explore specific details, it can provide type specific