From: Junio C Hamano <gitster@pobox.com>
Date: Thu, 28 Jun 2012 19:51:43 GMT
Subject: Re: [PATCH 1/2] difftool: only copy back files modified during directory diff
Message-ID: <7vbok35i5s.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1340912395-16990-1-git-send-email-tim.henigan@gmail.com>

Tim Henigan <tim.henigan@gmail.com> writes:

> When 'difftool --dir-diff' is used to compare working tree files,
> it always copies files from the tmp dir back to the working tree
> when the diff tool is closed, even if the files were not modified
> by the diff tool.
>
> This causes the file timestamp to change. Files should only be
> copied from the tmp dir back to the working copy if they were
> actually modified.
>
> Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
> ---
>
> This patch must be applied after commit 304970d on next (diff-no-index:
> exit(1) if 'diff --quiet <repo file> <external file>' finds changes).
> because it relies on 'git diff --quiet' to compare files outside the
> repository.
>
>
>  git-difftool.perl | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/git-difftool.perl b/git-difftool.perl
> index ae1e052..679a56d 100755
> --- a/git-difftool.perl
> +++ b/git-difftool.perl
> @@ -336,8 +336,11 @@ if (defined($dirdiff)) {
>  	# files were modified during the diff, then the changes
>  	# should be copied back to the working tree
>  	for my $file (@working_tree) {
> -		copy("$b/$file", "$workdir/$file") or die $!;
> -		chmod(stat("$b/$file")->mode, "$workdir/$file") or die $!;
> +		if ((-e "$b/$file") &&
> +		    (system('git', 'diff', '--quiet', "$b/$file", "$workdir/$file") != 0)) {

Why waste cycles to spawn "git diff" when you only want to find if
they are byte-for-byte identical *and* when you are importing many
perl modules from File::* already into the script?

> +			copy("$b/$file", "$workdir/$file") or die $!;
> +			chmod(stat("$b/$file")->mode, "$workdir/$file") or die $!;
> +		}
>  	}
>  } else {
>  	if (defined($prompt)) {