plone.app.discussion/plone/app/discussion/upgrades.zcml

<configure
    xmlns="http://namespaces.zope.org/zope"
    xmlns:genericsetup="http://namespaces.zope.org/genericsetup">

  <genericsetup:upgradeStep
      source="*"
      destination="100"
      title="Update plone.app.discussion setting registry"
      description=""
      profile="plone.app.discussion:default"
      handler=".upgrades.update_registry"
      />

  <genericsetup:upgradeStep
      title="edit comments and delete own comments"
      description="reload registry config to enable new fields edit_comment_enabled and delete_own_comment_enabled"
      source="100"
      destination="101"
      handler=".upgrades.update_registry"
      sortkey="1"
      profile="plone.app.discussion:default"
      />

  <genericsetup:upgradeStep
      title="delete comments and delete own comments"
      description="reload rolemap config to enable new permissions 'Delete comments' and 'Delete own comments'"
      source="101"
      destination="102"
      handler=".upgrades.update_rolemap"
      sortkey="1"
      profile="plone.app.discussion:default"
      />

  <genericsetup:upgradeSteps
      source="102"
      destination="1000"
      profile="plone.app.discussion:default">
    <!-- Apply the update rolemap step again, to avoid missing it when
         updating from plone.app.discussion 2.2.x.  When originally
         adding this step in the 2.3.x release, we should have made a
         bigger metadata revision increase to leave some room for new
         upgrade steps in 2.2.x. -->
    <genericsetup:upgradeStep
        title="delete comments and delete own comments"
        description="reload rolemap config to enable new permissions 'Delete comments' and 'Delete own comments'"
        handler=".upgrades.update_rolemap"
        />
    <genericsetup:upgradeStep
        title="Update plone.app.discussion workflows"
        handler=".upgrades.upgrade_comment_workflows"
        />
  </genericsetup:upgradeSteps>

  <genericsetup:upgradeSteps
      source="1000"
      destination="1001"
      profile="plone.app.discussion:default">
    <genericsetup:upgradeStep
        title="Move comment.js into plone-legacy bundle"
        description=""
        handler=".upgrades.add_js_to_plone_legacy"
        />
  </genericsetup:upgradeSteps>

  <genericsetup:upgradeSteps
    source="1001"
    destination="1002"
    profile="plone.app.discussion:default">
    <genericsetup:upgradeStep
        title="Extended review workflow with states pending, published and new: rejected and spam"
        description="Additional states allows moderator to review history of publishing and rejection"
        handler=".upgrades.extend_review_workflow"
        />
  </genericsetup:upgradeSteps>

  <genericsetup:upgradeDepends
      source="1002"
      destination="1003"
      profile="plone.app.discussion:default"
      title="Update controlpanel icon"
      import_steps="controlpanel" />

    <genericsetup:upgradeDepends
      source="1003"
      destination="1004"
      profile="plone.app.discussion:default"
      title="Add 'View comments' permission"
      import_steps="controlpanel" />



</configure>