[PATCH] crecord: fix issue when backgrounding editor would leave artefact

[Laurent Charignon]

This one should have the right whitespaces. 
Let me know if you have an issue and I will resend it.

Thanks,

> On Jul 16, 2015, at 11:53 AM, lc2817 at columbia.edu wrote:
> 
> # HG changeset patch
> # User Laurent Charignon <l.charignon at gmail.com>
> # Date 1437017963 25200
> #      Wed Jul 15 20:39:23 2015 -0700
> # Node ID aacc79aaf710f69c3e060920bcf3255d88640a87
> # Parent  35fa7c77c754aa4d156c42abfdb61ca178468872
> crecord: fix issue when backgrounding editor would leave artefact
> 
> Before this patch:
> - if a user was entering a commit message after having ran the curses
> interface
> - and then uses ctrl-z, followed by fg to put the editor in the
> background/foreground
> - then the curses interface would leave artefact on the screen of
> the editor, making entering the commit message a difficult task
> 
> This happened because ncurses registers a signal handler for SIGTSTP and
> does not restore the original signal handler after running.
> More info at:
> https://urldefense.proofpoint.com/v1/url?u=http://stackoverflow.com/questions/31440392/&k=ZVNjlDMF0FElm4dQtryO4A%3D%3D%0A&r=ovX3wDZmWBc057vX%2Bdkir5laRYh0DpiaFZ0DBnnb7ps%3D%0A&m=OCE9afx62pea7VZjYG1bpacqkMoTJeLGCxE2fMkZk38%3D%0A&s=c7f2e521ce6bc776bf01567dc9c39a8231aa344507b8297f28acc59907885350
> curses-wrapper-messing-up-terminal-after-background-foreground-sequence/
> 31441709#31441709
> 
> This patch restores the original value of the signal handler after
> running the curses interface and therefore fixes this issue.
> It don't know how to add a test for this issue, I tested the scenario
> above manually and it works correctly with the patch.
> 
> diff -r 35fa7c77c754 -r aacc79aaf710 mercurial/crecord.py
> --- a/mercurial/crecord.py	Sun Jul 12 17:59:25 2015 +0900
> +++ b/mercurial/crecord.py	Wed Jul 15 20:39:23 2015 -0700
> @@ -482,7 +482,10 @@
>     """
>     ui.write(_('starting interactive selection\n'))
>     chunkselector = curseschunkselector(headerlist, ui)
> +    f = signal.getsignal(signal.SIGTSTP)
>     curses.wrapper(chunkselector.main)
> +    # ncurses does not restore signal handler for SIGTSTP
> +    signal.signal(signal.SIGTSTP, f)
> 
> def testdecorator(testfn, f):
>     def u(*args, **kwargs):
> 
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