FIX: Don't notify of duplicate links on edit of the first post

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

@@ -111,9 +111,13 @@ export default Ember.Controller.extend({
     },
 
     afterRefresh($preview) {
-
+      const topic = this.get('model.topic');
       const linkLookup = this.get('linkLookup');
-      if (linkLookup) {
+      if (!topic || !linkLookup) { return; }
+
+      // Don't check if there's only one post
+      if (topic.get('posts_count') === 1) { return; }
+
       const post = this.get('model.post');
       if (post && post.get('user_id') !== this.currentUser.id) { return; }
 
@@ -127,7 +131,7 @@ export default Ember.Controller.extend({
             const body = I18n.t('composer.duplicate_link', {
               domain: info.domain,
               username: info.username,
-                post_url: info.post_url,
+              post_url: topic.urlForPostNumber(info.post_number),
               ago: relativeAge(moment(info.posted_at).toDate(), { format: 'medium' })
             });
             this.appEvents.trigger('composer-messages:create', {
@@ -140,7 +144,6 @@ export default Ember.Controller.extend({
         }
         return true;
       });
-      }
     },
 
     toggleWhisper() {

app/assets/javascripts/discourse/lib/link-lookup.js.es6

@@ -16,8 +16,8 @@ export default class LinkLookup {
 
     const linkInfo = this._links[normalized];
     if (linkInfo) {
-      // Skip edits to the same URL
-      if (post && post.get('url') === linkInfo.post_url) { return NO_RESULT; }
+      // Skip edits to the same post
+      if (post && post.get('post_number') === linkInfo.post_number) { return NO_RESULT; }
 
       _warned[href] = true;
       _warned[normalized] = true;

app/models/topic_link.rb

@@ -232,8 +232,8 @@ class TopicLink < ActiveRecord::Base
       normalized = tl.url.downcase.sub(/^https?:\/\//, '').sub(/\/$/, '')
       lookup[normalized] = { domain: tl.domain,
                              username: tl.post.user.username_lower,
-                             post_url: tl.post.url,
-                             posted_at: tl.post.created_at }
+                             posted_at: tl.post.created_at,
+                             post_number: tl.post.post_number }
     end
 
     lookup