MM-35128 CRT: Global Threads item should not be affected by 'mark as unread' in channel (#17505)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/channel.go

@@ -2389,9 +2389,9 @@ func (a *App) MarkChannelAsUnreadFromPost(postID string, userID string) (*model.
 		}
 
 		threadMembership, _ := a.Srv().Store.Thread().GetMembershipForUser(user.Id, threadId)
+		// if this post was not followed before, create thread membership and update mention count
 		if threadMembership == nil {
 			threadMembership, _ = a.Srv().Store.Thread().MaintainMembership(user.Id, threadId, true, true, true, true, false)
-		}
 			threadData, _ := a.Srv().Store.Thread().Get(threadId)
 			if threadData != nil && threadMembership != nil && threadMembership.Following {
 				channel, nErr := a.Srv().Store.Channel().Get(post.ChannelId, true)
@@ -2423,6 +2423,8 @@ func (a *App) MarkChannelAsUnreadFromPost(postID string, userID string) (*model.
 			}
 		}
 
+	}
+
 	channelUnread, nErr := a.Srv().Store.Channel().UpdateLastViewedAtPost(post, userID, unreadMentions, unreadMentionsRoot, *a.Config().ServiceSettings.ThreadAutoFollow)
 	if nErr != nil {
 		return channelUnread, model.NewAppError("MarkChannelAsUnreadFromPost", "app.channel.update_last_viewed_at_post.app_error", nil, nErr.Error(), http.StatusInternalServerError)

store/sqlstore/channel_store.go

@@ -2289,7 +2289,7 @@ func (s SqlChannelStore) UpdateLastViewedAtPost(unreadPost *model.Post, userID s
 	}
 
 	if updateThreads {
-		s.Thread().UpdateUnreadsByChannel(userID, threadsToUpdate, unreadDate, true)
+		s.Thread().UpdateUnreadsByChannel(userID, threadsToUpdate, unreadDate, false)
 	}
 	return result, nil
 }