clone: check update rev for being True
In 30be3aeb5344, there was an attempt to fallback to looking up the update
revision assuming it was always a rev but the documentation states:
True means update to default rev, anything else is treated as a revision
Therefore, we should only fallback to looking up the update rev if it is not
True. This bug was found in hg-git and I couldn't think of a test that does
this in pure Mercurial since the source repository is checked for the revision
as well (and therefore gracefully falls back).
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.