log: add bookmark option to "hg log"
Before pushing a bookmark with "hg push origin -B 'my-topic'", it is useful to inspect
the list of commits that are ancestors of the bookmark.
By relying on scmutil.bookmarkrevs(), "hg log -B topic" has the same bookmark semantics
found in other commands like hg export, hg email, hg strip.
Differential Revision: https://phab.mercurial-scm.org/D9341
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.