revlog: compute correct deltaparent in the deltaparent function
It now returns nullrev for chain base revisions, since they are conceptually
deltas against nullrev. The revdiff function was updated accordingly.
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.