Ensure that the html generator uses correct plural collection

If the plural and singular term are the same when generating a resource,
the template expects a `_collection` value to be set, however this was
only being set by the live generators and not the html generators.

This commect uses the correct `schema.collection` value when generating
a controller.

This closes #5562

priv/templates/phx.gen.html/controller.ex

@@ -6,7 +6,7 @@ defmodule <%= inspect context.web_module %>.<%= inspect Module.concat(schema.web
 
   def index(conn, _params) do
     <%= schema.plural %> = <%= inspect context.alias %>.list_<%= schema.plural %>()
-    render(conn, :index, <%= schema.plural %>: <%= schema.plural %>)
+    render(conn, :index, <%= schema.collection %>: <%= schema.plural %>)
   end
 
   def new(conn, _params) do

test/mix/tasks/phx.gen.html_test.exs

@@ -324,6 +324,15 @@ defmodule Mix.Tasks.Phx.Gen.HtmlTest do
     end)
   end
 
+  test "with a matching plural and singular term", config do
+    in_tmp_project(config.test, fn ->
+      Gen.Html.run(~w(Tracker Series series value:integer))
+      assert_file("lib/phoenix_web/controllers/series_controller.ex", fn file ->
+        assert file =~ "render(conn, :index, series_collection: series)"
+      end)
+    end)
+  end
+
   test "with --no-context no warning is emitted when context exists", config do
     in_tmp_project(config.test, fn ->
       Gen.Html.run(~w(Blog Post posts title:string))