Re: [RFC] git-format-patch: default to --from to avoid spoofed mails?

From: Jeff King <peff@peff.net>
Date: Jul 28, 2016, 21:56 UTC
Message-ID: <20160728215603.GA22865@sigill.intra.peff.net>
In-Reply-To: <xmqq8twlqwan.fsf@gitster.mtv.corp.google.com>

On Thu, Jul 28, 2016 at 02:37:04PM -0700, Junio C Hamano wrote:

Show 24 quoted lines

> Josh Triplett <josh@joshtriplett.org> writes:
> 
> > I'd like to propose changing the default behavior of git-format-patch to
> > --from (and adding a --from-author option to override, and perhaps a
> > config setting).  This will not change the output *except* when
> > formatting patches authored by someone else.  git-am and git-send-email
> > both handle the --from format without any issues.
> 
> I see this in "format-patch --help":
> 
>            Note that this option is only useful if you are actually
>            sending the emails and want to identify yourself as the
>            sender, but retain the original author (and git am will
>            correctly pick up the in-body header).  Note also that
>            git send-email already handles this transformation for
>            you, and this option should not be used if you are
>            feeding the result to git send-email.
> 
> The first one says "only useful", but it seems what it really means
> is "it becomes no-op if you are sending your own patch anyway".  So
> that one does not worry me.  What is most worrysome is the latter
> half of the last sentence.  Is it really "should not be", or is it
> merely "use of this option is just a waste of time, as you would get
> exactly the same result anyway"?  If it is the latter, that is fine.

It does what you want, and omits the in-body header when it would be redundant.

I think the original reason I did not make "--from" the default is that I was worried about breaking consumers which do not know how to handle in-body headers. "git am" knows how to handle them, but if you have a one-off script that parses only the mail headers, it will start claiming you as the author of every patch.

E.g., if you do:

  git format-patch -o output ...
  grep -hm1 ^From: output/*

right now that gets you a list of patch authors. With "--from", it would return your name N times.

That's obviously a toy, but I wonder if people have scripts which behave similarly.

Another way to think about it is that "--from" is a no-brainer when you really are going to email the patches (and that's why it is has always been the default behavior in git-send-email). But if you _aren't_ going to mail the patches, retaining the original headers is more convenient. It's not clear to me how many non-mail users of format-patch there are (certainly rebase is one of them, but because it uses "am" on the receiving side, I think everything should Just Work).

-Peff