Log Message:
textproc/ruby-asciidoctor: update to 2.0.15

2.0.15 (2021-04-27)
Bug Fixes

* Don't include trailing period, question mark, or exclamation point in
  target (URL) of autolink (#3860)
* Don't assign nil value to named attribute mapped to absent positional
  attribute when parsing attrlist (#4033)
* Remove leading and trailing spaces around role on inline phrase (#4035)
* Ignore empty role on inline phrase defined using legacy syntax and
  followed by comma (#4035)
* Use xreftext on document as fallback link text in HTML output for
  inter-document xref that resolves to current document when no link text is
  provided (#4032)
* Use xreftext on document as fallback link text in HTML output for internal
  xref with empty fragment when no link text is provided (#4032)
* Use document ID as linkend in DocBook output for internal xref with empty
  fragment; auto-generating one if necessary (#4032)

Improvements

* Format keyboard references in monospace in manpage output

Build / Infrastructure

* Get remaining invoker tests working on JRuby 9.1 for Windows