[PATCH stable] progress: disable progress when the terminal resembles cmd.exe (issue4801)

[Augie Fackler]

> On Mar 1, 2016, at 11:35, Augie Fackler <raf at durin42.com> wrote:
> 
> # HG changeset patch
> # User Augie Fackler <augie at google.com>
> # Date 1456860899 18000
> #      Tue Mar 01 14:34:59 2016 -0500
> # Branch stable
> # Node ID 30732f02af820e8851163e5ec177e3c3d038eb08
> # Parent  5f95d6a70e9b37bf11487580a5c750d861baa8f5
> # EXP-Topic progress-cmd
> progress: disable progress when the terminal resembles cmd.exe (issue4801)

I fail at patches, discard this and a v2 will follow soon.

> 
> It appears that cmd.exe is hopelessly unreliable when it comes to
> handling carriage returns, based on my own web searching. The blessed
> mechanism for performing cursor positioning appears to be
> SetConsoleCursorPosition(), but I don't have easy access to a Windows
> machine, and we need a simple fix for stable anyway.
> 
> Ideally, someone on Windows can write a fix for this and contribute it.
> 
> diff --git a/mercurial/progress.py b/mercurial/progress.py
> --- a/mercurial/progress.py
> +++ b/mercurial/progress.py
> @@ -18,8 +18,17 @@ def spacejoin(*args):
>     return ' '.join(s for s in args if s)
> 
> def shouldprint(ui):
> -    return not (ui.quiet or ui.plain()) and (
> -        ui._isatty(sys.stderr) or ui.configbool('progress', 'assume-tty'))
> +    if ui.configbool('progress', 'assume-tty'):
> +        return True
> +    if os.name == 'nt' and 'TERM' not in os.environ:
> +        # We think this is cmd.exe, which means we're going to skip
> +        # progress. It appears that carriage returns are unreliable
> +        # for cursor positioning in cmd.exe, and that we should
> +        # instead be using SetConsoleCursorPosition() to move the
> +        # cursor for progress writes. See issue4801 for the report
> +        # that revealed this problem.
> +        return False
> +    return not (ui.quiet or ui.plain()) and ui._isatty(sys.stderr)
> 
> def fmtremaining(seconds):
>     """format a number of remaining seconds in human readable way
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