revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/Documentation/asciidoctor-extensions.rb

@@ -9,11 +9,8 @@ module Git
       named :chrome
 
       def process(parent, target, attrs)
-        prefix = parent.document.attr('git-relative-html-prefix')
-        if parent.document.doctype == 'book'
-          "<ulink url=\"#{prefix}#{target}.html\">" \
-          "#{target}(#{attrs[1]})</ulink>"
-        elsif parent.document.basebackend? 'html'
+        if parent.document.basebackend? 'html'
+          prefix = parent.document.attr('git-relative-html-prefix')
           %(<a href="#{prefix}#{target}.html">#{target}(#{attrs[1]})</a>)
         elsif parent.document.basebackend? 'docbook'
           "<citerefentry>\n" \
@@ -23,26 +20,9 @@ module Git
         end
       end
     end
-
-    class DocumentPostProcessor < Asciidoctor::Extensions::Postprocessor
-      def process document, output
-        if document.basebackend? 'docbook'
-          mansource = document.attributes['mansource']
-          manversion = document.attributes['manversion']
-          manmanual = document.attributes['manmanual']
-          new_tags = "" \
-            "<refmiscinfo class=\"source\">#{mansource}</refmiscinfo>\n" \
-            "<refmiscinfo class=\"version\">#{manversion}</refmiscinfo>\n" \
-            "<refmiscinfo class=\"manual\">#{manmanual}</refmiscinfo>\n"
-          output = output.sub(/<\/refmeta>/, new_tags + "</refmeta>")
-        end
-        output
-      end
-    end
   end
 end
 
 Asciidoctor::Extensions.register do
   inline_macro Git::Documentation::LinkGitProcessor, :linkgit
-  postprocessor Git::Documentation::DocumentPostProcessor
 end