Fix erb linting errors and remove unnecessary code (#1449)

Co-authored-by: Sutou Kouhei <[email protected]>

Author: st0012

lib/rdoc/generator/template/darkfish/_head.rhtml

@@ -16,13 +16,8 @@
   <meta name="description" content="<%= h "#{file.page_name}: #{excerpt(file.comment)}" %>">
 <%- elsif @title %>
   <meta name="keywords" content="ruby,documentation,<%= h @title %>">
-
-  <%- if @options.main_page and
-      main_page = @files.find { |f| f.full_name == @options.main_page } then %>
-    <meta name="description" content="<%= h "#{@title}: #{excerpt(main_page.comment)}" %>">
-  <%- else %>
-    <meta name="description" content="Documentation for <%= h @title %>">
-  <%- end %>
+<% description = @main_page ? "#{@title}: #{excerpt(@main_page.comment)}" : "Documentation for #{@title}" %>
+  <meta name="description" content="<%= h description %>">
 <%- end %>
 
 <%- if canonical_url = @options.canonical_root %>

lib/rdoc/generator/template/darkfish/_sidebar_search.rhtml

@@ -4,6 +4,7 @@
       <input id="search-field" role="combobox" aria-label="Search"
              aria-autocomplete="list" aria-controls="search-results"
              type="text" name="search" placeholder="Search (/) for a class, method, ..." spellcheck="false"
+             autocomplete="off"
              title="Type to search, Up and Down to navigate, Enter to load">
     </div>
 

lib/rdoc/generator/template/darkfish/table_of_contents.rhtml

@@ -47,7 +47,7 @@
    unless table.empty? then %>
     <ul>
 <%- table.each do |item| %>
-<%-   label = item.respond_to?(:label) ? item.label(klass) : item.aref %>
+  <%- label = item.respond_to?(:label) ? item.label(klass) : item.aref %>
       <li><a href="<%= klass.path %>#<%= label %>"><%= item.plain_html %></a></li>
 <%- end %>
     </ul>