contrib: add showstack extension
This allows getting a Python stack trace at any time on Unix by
hitting Ctrl-\ (or Ctrl-T on BSDs). Useful for debugging mysterious
hangs on the fly. Sample output:
$ hg log -k nosuchmessage
^\
File "/home/mpm/hg/mercurial/revset.py", line 3089, in _iterfilter
if cond(x):
File "/home/mpm/hg/mercurial/util.py", line 415, in f
cache[arg] = func(arg)
File "/home/mpm/hg/mercurial/revset.py", line 1215, in matches
for t in c.files() + [c.user(), c.description()])
File "/home/mpm/hg/mercurial/context.py", line 525, in files
return self._changeset[3]
File "/home/mpm/hg/mercurial/util.py", line 531, in __get__
result = self.func(obj)
File "/home/mpm/hg/mercurial/context.py", line 498, in _changeset
return self._repo.changelog.read(self.rev())
File "/home/mpm/hg/mercurial/changelog.py", line 338, in read
text = self.revision(node)
File "/home/mpm/hg/mercurial/revlog.py", line 1092, in revision
bins = self._chunks(chain)
File "/home/mpm/hg/mercurial/revlog.py", line 1013, in _chunks
ladd(decompress(buffer(data, chunkstart - offset, chunklength)))
File "/home/mpm/hg/mercurial/revlog.py", line 91, in decompress
return _decompress(bin)
----
copyright (c) 2006-2010 David JEAN LOUIS
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