util: introduce util.debugstacktrace for showing a stack trace without crashing This is often very handy when hacking/debugging. Calling util.debugstacktrace('hey') from a place in hg will give something like: hey at: ./hg:38 in <module> /home/user/hgsrc/mercurial/dispatch.py:28 in run /home/user/hgsrc/mercurial/dispatch.py:65 in dispatch /home/user/hgsrc/mercurial/dispatch.py:88 in _runcatch /home/user/hgsrc/mercurial/dispatch.py:740 in _dispatch /home/user/hgsrc/mercurial/dispatch.py:514 in runcommand /home/user/hgsrc/mercurial/dispatch.py:830 in _runcommand /home/user/hgsrc/mercurial/dispatch.py:801 in checkargs /home/user/hgsrc/mercurial/dispatch.py:737 in <lambda> /home/user/hgsrc/mercurial/util.py:472 in check ...