commit: search both parents for missing copy revision (
issue2484)
raise a proper abort if we can't find an ancestor
Mercurial's documentation is kept in reStructuredText format, which is
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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.