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logtoprocess: avoid traceback when running long commands

Authored by valentin.gatienbaron on Mar 2 2020, 3:00 PM.



$ hg log -r "present($(yes | tr -d '\n' | head -c 130000))" "$(yes | tr -d '\n' | head -c 5000)" --config extensions.logtoprocess= --config logtoprocess.commandfinish=whatever
Traceback (most recent call last):

File "/usr/bin/hg", line 67, in <module>
File "/usr/lib64/python2.7/site-packages/mercurial/", line 111, in run
  status = dispatch(req)
File "/usr/lib64/python2.7/site-packages/mercurial/", line 290, in dispatch
File "/usr/lib64/python2.7/site-packages/mercurial/", line 1991, in log
  logger.log(self, event, msg, opts)
File "/usr/lib64/python2.7/site-packages/hgext/", line 72, in log
  procutil.runbgcommand(script, fullenv, shell=True)
File "/usr/lib64/python2.7/site-packages/mercurial/utils/", line 597, in runbgcommand
  b'error running %r: %s' % (cmd, os.strerror(returncode)),

OSError: [Errno 7] error running 'whatever': Argument list too long

This can happen if you pass a bunch of filenames to hg commit, for instance.

This is due to a size limit on individual env vars (on linux, but I
imagine there are similar limits in other OSes):
$ FOO=$(yes | head -c 131000) /usr/bin/true
$ FOO=$(yes | head -c 132000) /usr/bin/true
-bash: /usr/bin/true: Argument list too long

I propose to avoid this by truncating the message. I didn't make the
limit configurable as it doesn't seem particularly convenient to
customize this. I'm not sure if various OSes would want radically
different limits here?

Diff Detail

rHG Mercurial
Automatic diff as part of commit; lint not applicable.
Automatic diff as part of commit; unit tests not applicable.