resolves github#519 enable source-to-source navigation for inter-docu…

…ment xrefs

- set outfilesuffix=.adoc so inter-document xref links are created between AsciiDoc files

Gemfile

@@ -10,5 +10,5 @@ gem "rdoc", "~>3.6"
 gem "org-ruby", "= 0.9.9"
 gem "creole", "~>0.3.6"
 gem "wikicloth", "=0.8.3"
-gem "asciidoctor", "= 1.5.2"
+gem "asciidoctor", "= 1.5.5"
 gem "rake"

lib/github/markups.rb

@@ -29,7 +29,7 @@
 
 markup(::GitHub::Markups::MARKUP_ASCIIDOC, :asciidoctor, /adoc|asc(iidoc)?/, ["AsciiDoc"]) do |content|
   Asciidoctor::Compliance.unique_id_start_index = 1
-  Asciidoctor.convert(content, :safe => :secure, :attributes => %w(showtitle=@ idprefix idseparator=- env=github env-github source-highlighter=html-pipeline))
+  Asciidoctor.convert(content, :safe => :secure, :attributes => %w(showtitle=@ idprefix idseparator=- outfilesuffix=.adoc env=github env-github source-highlighter=html-pipeline))
 end
 
 command(

test/markups/README.asciidoc

@@ -7,6 +7,8 @@
 
 Refer to <<another-section>> or <<another-section-1>>.
 
+Navigate to <<another-document#,another document>>.
+
 == Another Section
 
 NOTE: Here is some source code.

test/markups/README.asciidoc.html

@@ -15,6 +15,9 @@ <h2>First Section</h2>
 <div>
 <p>Refer to <a href="#another-section">Another Section</a> or <a href="#another-section-1">Another Section</a>.</p>
 </div>
+<div>
+<p>Navigate to <a href="another-document.adoc">another document</a>.</p>
+</div>
 </div>
 </div>
 <div>