FEATURE: move a topic from PM to regular topic or vice versa

app/assets/javascripts/discourse/controllers/topic.js.es6

@@ -545,6 +545,14 @@ export default Ember.Controller.extend(SelectedPostsCount, BufferedContent, {
     changePostOwner(post) {
       this.get('selectedPosts').addObject(post);
       this.send('changeOwner');
+    },
+
+    convertToPublicTopic() {
+      this.get('content').convertTopic("public");
+    },
+
+    convertToPrivateMessage() {
+      this.get('content').convertTopic("private");
     }
   },
 

app/assets/javascripts/discourse/models/topic.js.es6

@@ -4,6 +4,7 @@ import { propertyEqual } from 'discourse/lib/computed';
 import { longDate } from 'discourse/lib/formatter';
 import computed from 'ember-addons/ember-computed-decorators';
 import ActionSummary from 'discourse/models/action-summary';
+import { popupAjaxError } from 'discourse/lib/ajax-error';
 
 export function loadTopicView(topic, args) {
   const topicId = topic.get('id');
@@ -446,8 +447,13 @@ const Topic = RestModel.extend({
     }).finally(()=>this.set('archiving', false));
 
     return promise;
-  }
+  },
 
+  convertTopic(type) {
+    return Discourse.ajax(`/t/${this.get('id')}/convert-topic/${type}`, {type: 'PUT'}).then(() => {
+      window.location.reload();
+    }).catch(popupAjaxError);
+  }
 });
 
 Topic.reopenClass({

app/assets/javascripts/discourse/templates/topic.hbs

@@ -256,6 +256,16 @@
       {{/if}}
     </li>
 
+    {{#if currentUser.admin}}
+      <li class="topic-admin-convert">
+        {{#if model.isPrivateMessage}}
+          {{d-button action="convertToPublicTopic" icon="comment" label="topic.actions.make_public"}}
+        {{else}}
+          {{d-button action="convertToPrivateMessage" icon="envelope" label="topic.actions.make_private"}}
+        {{/if}}
+      </li>
+    {{/if}}
+
     {{plugin-outlet "topic-admin-menu-buttons"}}
   {{/popup-menu}}
 {{/if}}

app/assets/javascripts/discourse/widgets/post-small-action.js.es6

@@ -20,7 +20,9 @@ const icons = {
   'visible.disabled': 'eye-slash',
   'split_topic': 'sign-out',
   'invited_user': 'plus-circle',
-  'removed_user': 'minus-circle'
+  'removed_user': 'minus-circle',
+  'public_topic': 'comment',
+  'private_topic': 'envelope'
 };
 
 export default createWidget('post-small-action', {