tags: add /tag_versions page.

app/controllers/tag_versions_controller.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+class TagVersionsController < ApplicationController
+  respond_to :html, :xml, :json
+
+  def index
+    tag_id = params[:tag_id] || params[:search][:tag_id]
+    tag_name = params[:search][:name_matches]
+    updater_id = params[:updater_id] || params[:search][:updater_id]
+    updater_name = params[:search][:updater_name]
+
+    @tag = Tag.find(tag_id) if tag_id
+    @tag = Tag.find_by_name(tag_name) if tag_name
+    @updater = User.find(updater_id) if updater_id
+    @updater = User.find_by_name(updater_name) if updater_name
+
+    if request.format.html?
+      @tag_versions = authorize TagVersion.visible(CurrentUser.user).paginated_search(params, defaults: { tag_id: @tag&.id, updater_id: @updater&.id, order: "updated_at" }, count_pages: true)
+      @tag_versions = @tag_versions.includes(:tag, :updater, :previous_version)
+    else
+      @tag_versions = authorize TagVersion.visible(CurrentUser.user).paginated_search(params, defaults: { tag_id: @tag&.id, updater_id: @updater&.id })
+    end
+
+    respond_with(@tag_versions)
+  end
+
+  def show
+    @tag_version = authorize TagVersion.find(params[:id])
+
+    respond_with(@tag_version) do |format|
+      format.html { redirect_to tag_versions_path(search: { id: @tag_version.id }) }
+    end
+  end
+end