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
...
This makes it possible to do lock validation as part of a normal test
run. I didn't attempt any wlock validation because that's a bit more
subtle to detect properly. Thanks to the initial patch from Mads for
the idea.