tag: warn users about tag/branch possible name conflicts
As reported recently, Mercurial users can easily find confusion when
using a common name for a tag and a branch. It seems reasonable to warn
them about this potential outcome, to avoid that "surprise".
* Explain briefly the issue in "hg help tag"
* Warn when tagging a revision
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.