doc/README

hgtagsfnodescache: handle nullid lookup

The null revision is empty, so it `.hgtags` content is `nullid` in regards with
the `hgtagsfnodescache`. Dealing with `nullid` will help with the next
changeset. Before this change, feeding `nullid` to `hgtagsfnodescache.getfnode` would
return a wrong result (fnode for tip).

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.