dagparser: parses and formats DAGs as concise text
As discussed during the sprint. See the doc comment and doctests
for specification and examples. This is used in subsequent patches
to export revlog and changelog DAGs, and to generate a repo with
a given changelog DAG.
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.