contrib/showstack.py

tests: work around libmagic bug in svn subrepo tests

libmagic 5.40 introduced a bug [1] wherein ASCII text files with fewer
than 3 distinct character values would be reported as binary data
rather than as text. This bug was later fixed in version 5.41 [2].

SVN uses libmagic to determine the MIME type of added files with missing
or unknown extensions [3]. This results in test failures on systems with
libmagic 5.40 installed:

   $ echo a > a
   $ svn add a
-  A         a
+  A  (bin)  a

A simple workaround is to change the test file's content to include
3 distinct ASCII values (including the terminating newline).

[1] https://bugs.astron.com/view.php?id=180
[2] https://bugs.astron.com/view.php?id=261
[3] https://svnbook.red-bean.com/en/1.8/svn.advanced.props.html#idm2649

# showstack.py - extension to dump a Python stack trace on signal
#
# binds to both SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)
r"""dump stack trace when receiving SIGQUIT (Ctrl-\) or SIGINFO (Ctrl-T on BSDs)
"""

import signal
import sys
import traceback


def sigshow(*args):
    sys.stderr.write("\n")
    traceback.print_stack(args[1], limit=10, file=sys.stderr)
    sys.stderr.write("----\n")


def sigexit(*args):
    sigshow(*args)
    print('alarm!')
    sys.exit(1)


def extsetup(ui):
    signal.signal(signal.SIGQUIT, sigshow)
    signal.signal(signal.SIGALRM, sigexit)
    try:
        signal.signal(signal.SIGINFO, sigshow)
    except AttributeError:
        pass