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

[Jun Wu]

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)