State debconf.set_file now accepts a template as a file

It follows the same convention as `file.managed` for example.

This also introduces a new function in the `debconfmod` module to set the
Debconf selections from a template or, as before, from a simple file.

Fixes #7331

salt/modules/debconfmod.py

@@ -133,6 +133,42 @@ def set_(package, question, type, value, *extra):
     return True
 
 
+def set_template(path, template, context, defaults, saltenv='base', **kwargs):
+    '''
+    Set answers to debconf questions from a template.
+
+    path
+        location of the file containing the package selections
+
+    template
+        template format
+
+    context
+        variables to add to the template environment
+
+    default
+        default values for the template environment
+
+    CLI Example:
+
+    .. code-block:: bash
+
+        salt '*' debconf.set_template salt://pathto/pkg.selections.jinja jinja None None
+
+    '''
+
+    path = __salt__['cp.get_template'](
+        path=path,
+        dest=None,
+        template=template,
+        saltenv=saltenv,
+        context=context,
+        defaults=defaults,
+        **kwargs)
+
+    return set_file(path, saltenv, **kwargs)
+
+
 def set_file(path, saltenv='base', **kwargs):
     '''
     Set answers to debconf questions from a file.

salt/states/debconfmod.py

@@ -57,9 +57,9 @@ def __virtual__():
     return __virtualname__
 
 
-def set_file(name, source, **kwargs):
+def set_file(name, source, template=None, context=None, defaults=None, **kwargs):
     '''
-    Set debconf selections from a file
+    Set debconf selections from a file or a template
 
     .. code-block:: yaml
 
@@ -71,20 +71,56 @@ def set_file(name, source, **kwargs):
           debconf.set_file:
             - source: salt://pathto/pkg.selections?saltenv=myenvironment
 
+        <state_id>:
+          debconf.set_file:
+            - source: salt://pathto/pkg.selections.jinja2
+            - template: jinja2
+            - context:
+                some_value: "false"
+
     source:
         The location of the file containing the package selections
+
+    template
+        If this setting is applied then the named templating engine will be
+        used to render the package selections file, currently jinja, mako, and
+        wempy are supported
+
+    context
+        Overrides default context variables passed to the template.
+
+    defaults
+        Default context passed to the template.
     '''
     ret = {'name': name,
            'changes': {},
            'result': True,
            'comment': ''}
 
+    if context is None:
+        context = {}
+    elif not isinstance(context, dict):
+        return _error(
+            ret, 'Context must be formed as a dict')
+
+    if defaults is None:
+        defaults = {}
+    elif not isinstance(defaults, dict):
+        return _error(
+            ret, 'Defaults must be formed as a dict')
+
+
     if __opts__['test']:
         ret['result'] = None
         ret['comment'] = 'Debconf selections would have been set.'
         return ret
 
-    if __salt__['debconf.set_file'](source, **kwargs):
+    if template:
+        result = __salt__['debconf.set_template'](source, template, context, defaults, **kwargs)
+    else:
+        result = __salt__['debconf.set_file'](source, **kwargs)
+
+    if result:
         ret['comment'] = 'Debconf selections were set.'
     else:
         ret['result'] = False