Unofficial patch for asciidoctor-diagram-1.2.1

diagram.patch

--- diagram.rb.orig	2015-06-26 22:31:23.000000000 +0900
+++ diagram.rb	2015-06-26 22:31:52.000000000 +0900
@@ -114,7 +114,9 @@ module Asciidoctor
         target = attributes.delete('target')

         image_name = "#{target || ('diag-' + source.checksum)}.#{format}"
-        image_dir = File.expand_path(parent.document.attributes['imagesdir'] || '', parent.document.attributes['outdir'] || parent.document.attributes['docdir'])
+        outdir     = parent.document.attributes['outdir'] || parent.document.attributes['docdir']
+        imagesdir  = lambda {|s| outdir && s.chr == '/' ? s[1,s.length] : s}[(parent.document.attributes['imagesdir'] || '')]
+        image_dir  = File.expand_path(imagesdir, outdir)
         image_file = File.expand_path(image_name, image_dir)
         metadata_file = File.expand_path("#{image_name}.cache", image_dir)

diagram.rb is located in vendor/bundle/ruby/2.2.0/gems/asciidoctor-diagram-1.2.1/lib/asciidoctor-diagram/util.