From: Jeff King <peff@peff.net>
Date: Tue, 15 Mar 2011 01:32:23 GMT
Subject: Re: git-reset HEAD --permissions-only
Message-ID: <20110315013223.GB31865@sigill.intra.peff.net>
In-Reply-To: <illts0$c6q$1@dough.gmane.org>

On Mon, Mar 14, 2011 at 03:29:51PM -0500, Neal Kreitzinger wrote:

> Is there a way to only reset the file permissions of the working-tree
> to match HEAD file permissions without resetting the content of the
> files?

Not directly, but you could munge a patch to do so and apply it in
reverse. For example:

  git diff "$@" |
  perl -ne '
    if (/^diff/) { $diff = $_ }
    elsif (/^old mode/) { print $diff, $_ }
    elsif (/^new mode/) { print $_ }
  ' |
  git apply -R

Which seems a little more complicated than it needs to be, but we don't
(AFAIK) have a way to say "show me only the mode changes from this
diff in an applicable form". The closest would be "git diff --summary",
but you cannot directly apply it (and I would hesitate to recommend
parsing it).

You could also use "git checkout -p", which is designed for exactly this
sort of picking-apart of a patch, but it has no way to specify "say yes
to all of the mode changes, no to everything else"; you have to manually
approve each hunk. Which doesn't work if you have a lot of these files.

I guess for mode changes, you don't care if you chmod something that is
already fine. So yet another way to do it would be:

  git ls-files -sz |
  perl -0ne '
    /100(\d+).*?\t(.*)/ or next;
    -e $2 or next;
    chmod(oct($1), $2)
      or die "chmod failed: $!";
  '

Hope that helps,
-Peff