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Subject: Re: [PATCH] checkpatch: Allow not using -f with files that are in git
To:     Joe Perches <joe@perches.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Andy Whitcroft <apw@shadowen.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <45b81a48e1568bd0126a96f5046eb7aaae9b83c9.camel@perches.com>
From:   Rasmus Villemoes <linux@rasmusvillemoes.dk>
Message-ID: <234290e5-b8dc-22c7-d26f-60a02844ce0a@rasmusvillemoes.dk>
Date:   Tue, 25 Aug 2020 14:23:06 +0200
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On 25/08/2020 02.09, Joe Perches wrote:
> If a file exists in git and checkpatch is used without the -f
> flag for scanning a file, then checkpatch will scan the file
> assuming it's a patch and emit:
> 
> ERROR: Does not appear to be a unified-diff format patch
> 
> Change the behavior to assume the -f flag if the file exists
> in git.

Heh, I read the patch subject to mean you introduced a way for subsystem
maintainers to prevent running checkpatch -f on their files, which I
think some would like ;)

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 79fc357b18cd..cdee7cfadc11 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -976,6 +976,16 @@ sub seed_camelcase_includes {
>  	}
>  }
>  
> +sub git_is_single_file {
> +	my ($filename) = @_;
> +
> +	return 0 if ((which("git") eq "") || !(-e "$gitroot"));
> +
> +	my $output = `${git_command} ls-files -- $filename`;
> +	my $count = $output =~ tr/\n//;
> +	return $count eq 1 && $output =~ m{^${filename}$};
> +}

Isn't that somewhat expensive to do for each file? Why not postpone that
check till we're about to complain that the file is not a diff (haven't
looked at how such a refactoring would look).

Rasmus