[PATCH] dispatch: treat SIGPIPE as a termination signal (BC)

[Jun Wu]

Actually that's not a problem since the output is redirected to the pager
and it won't get printed out.

Excerpts from Jun Wu's message of 2017-02-07 12:17:00 -0800:
> This approach looks good to me. The only problem is it will print "killed!"
> on SIGPIPE so maybe a follow-up to make it silent.
> 
> Excerpts from Simon Farnsworth's message of 2017-02-07 12:08:29 -0800:
> > # HG changeset patch
> > # User Simon Farnsworth <simonfar at fb.com>
> > # Date 1486498104 28800
> > #      Tue Feb 07 12:08:24 2017 -0800
> > # Node ID e1150763706818fffa62c81a72a88574d20caea1
> > # Parent  1f51b4658f21bbb797e922d155c1046eddccf91d
> > dispatch: treat SIGPIPE as a termination signal (BC)
> > 
> > pager previously set SIGPIPE to immediately exit the process, ignoring any
> > Python @atexit handlers, exception handling etc - just instant termination.
> > 
> > Simply removing this as per changeset aaa751585325 meant that when you
> > aborted a long running pager command, Mercurial would not quit; instead, we
> > should add SIGPIPE to the list of termination signals in dispatch.py.
> > 
> > This is a slight BC break, as previously, a process that was piping data
> > into or out of Mercurial would not kill Mercurial if it died before closing
> > its end of the pipe, whereas it will now cause Mercurial to exit.
> > 
> > diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
> > --- a/mercurial/dispatch.py
> > +++ b/mercurial/dispatch.py
> > @@ -147,7 +147,7 @@
> >  
> >      ui = req.ui
> >      try:
> > -        for name in 'SIGBREAK', 'SIGHUP', 'SIGTERM':
> > +        for name in 'SIGBREAK', 'SIGHUP', 'SIGTERM', 'SIGPIPE':
> >              num = getattr(signal, name, None)
> >              if num:
> >                  signal.signal(num, catchterm)