Create locale helper for global translations

There are some translation strings we should use across multiple views.
Instead of duplicating the translations, we can use a different locale
helper method, `#tt`, to get a hash of all available translations.

Then, in a partial view like `pagination.mustache`, we can render
translations regardless of what the current view class is.

This commit adds the necessary helper, tests, and uses the new method to
render translations on the `pagination.mustache` template, which is used
by many other view classes (latest changes, history, and search).

lib/gollum/locales/en.yml

@@ -1,4 +1,11 @@
 en:
+  pagination:
+    aria:
+      label: Pagination
+      next_page: Next page
+      previous_page: Previous page
+    next: Next
+    previous: Previous
   precious/views/compare:
     back_to_page_history: Back to Page History
     back_to_top: Back to Top
@@ -12,13 +19,6 @@ en:
     browse_in_history_description: Browse the page at this point in the history
     compare_revisions: Compare Revisions
     history_for: History for
-    pagination:
-      aria:
-        label: Pagination
-        next_page: Next page
-        previous_page: Previous page
-      next: Next
-      previous: Previous
   precious/views/latest_changes:
     title: Latest Changes (Globally)
   precious/views/layout:
@@ -34,12 +34,5 @@ en:
       show_all: "Show all %{count} hits in this page"
     back_to_top: Back to Top
     no_results: There are no results for your search
-    pagination:
-      aria:
-        label: Pagination
-        next_page: Next page
-        previous_page: Previous page
-      next: Next
-      previous: Previous
     search_results_for: Search results for
     title: "Search results for %{query}"

lib/gollum/templates/pagination.mustache

@@ -1,23 +1,23 @@
-<nav class="paginate-container" aria-label="{{t.pagination.aria.label}}">
+<nav class="paginate-container" aria-label="{{tt.pagination.aria.label}}">
   <div class="pagination" id="pagination">
     <a
-      aria-label="{{t.pagination.aria.previous_page}}"
+      aria-label="{{td.pagination.aria.previous_page}}"
       class="previous_page {{^previous_page}}disabled{{/previous_page}}"
       href="?page_num={{previous_page}}{{query_string}}"
       id="prev"
       rel="prev"
     >
-      {{t.pagination.previous}}
+      {{tt.pagination.previous}}
     </a>
 
     <a
-      aria-label="{{t.pagination.aria.next_page}}"
+      aria-label="{{td.pagination.aria.next_page}}"
       class="next_page {{^next_page}}disabled{{/next_page}}"
       href="?page_num={{next_page}}{{query_string}}"
       id="next"
       rel="next"
     >
-      {{t.pagination.next}}
+      {{tt.pagination.next}}
     </a>
   </div>
 </nav>

lib/gollum/views/helpers/locale_helpers.rb

@@ -21,6 +21,13 @@ module Precious
         autofill I18n.t(locale_klass_name)
       end
 
+      # Returns all I18n translation strings from the root of an I18n YAML file.
+      # Otherwise, it works exactly like the `#t` method that's also defined in
+      # this file.
+      def tt
+        autofill I18n.t('.')
+      end
+
       private
 
       # Recursively looks up I18n translation values and autofills any YAML

test/gollum/views/test_locale_helper.rb

@@ -132,4 +132,99 @@ describe Precious::Views::LocaleHelpers do
       end
     end
   end
+
+  describe "#tt" do
+    describe "mustache usage" do
+      let(:subject) { dummy_instance.render(mustache_template) }
+
+      let(:mustache_template) { "{{ tt.test_class.hello_world }}" }
+
+      describe "in the default locale" do
+        it "returns the translation string" do
+          _(subject).must_equal "Hello world"
+        end
+      end
+
+      describe "in the configured locale" do
+        it "returns the translation string" do
+          I18n.locale = :de
+
+          _(subject).must_equal "Hallo Welt"
+        end
+      end
+
+      describe "translations with YAML arguments" do
+        let(:mustache_template) { "{{ tt.test_class.author_info.full }}" }
+
+        describe "in the default locale" do
+          it "autofills YAML arguments" do
+            _(subject).must_equal "Author J.R.R. is from Bloemfontein"
+          end
+        end
+
+        describe "in the configured locale" do
+          it "autofills YAML arguments" do
+            I18n.locale = :de
+
+            _(subject).must_equal "Autor J.R.R. ist vom Bloemfontein"
+          end
+        end
+      end
+
+      describe "translations with invalid arguments" do
+        let(:mustache_template) { "{{ tt.test_class.has_invalid_argument }}" }
+
+        it "fails gracefully with embedded error message" do
+          expected_string = "Welcome to " \
+            "[#{TestClass::NO_METHOD_MESSAGE}: no_matching_method]"
+
+          _(subject).must_equal expected_string
+        end
+      end
+
+      describe "missing translations" do
+        let(:mustache_template) {
+          "{{ tt.test_class.nested.nonexistent_key }}"
+        }
+
+        it "outputs an empty string" do
+          _(subject).must_be_empty
+        end
+      end
+    end
+
+    describe "usage" do
+      let(:subject) { dummy_instance.tt }
+
+      it "returns a hash" do
+        _(subject).must_be_kind_of Hash
+      end
+
+      it "returns all present translation keys" do
+        i18n_keys = I18n.t(".").keys
+
+        _(subject.keys).must_equal i18n_keys
+      end
+
+      it "returns nested keys" do
+        nested_keys = subject[:test_class][:author_info].keys
+
+        _(nested_keys).must_equal [:full]
+      end
+
+      describe "auto-filled YAML arguments" do
+        let(:subject) { dummy_instance.tt[:test_class][:author_info][:full] }
+
+        it "auto-fills in the default locale" do
+          _(subject).must_equal "Author J.R.R. is from Bloemfontein"
+        end
+
+        it "auto-fills in a configured locale" do
+          I18n.locale = :de
+
+          _(subject).must_equal "Autor J.R.R. ist vom Bloemfontein"
+        end
+      end
+    end
+  end
 end