Re: [Qemu-devel] [PATCH v6 0/4] 9p: Fix file ID collisions

[Christian Schoenebeck via Qemu-devel <qemu-devel@nongnu.org>]

On Mittwoch, 4. September 2019 15:02:30 CEST Christian Schoenebeck wrote:
> > > Well, mailman is handling this correctly. It replaces the "From:" field
> > > with a placeholder and instead adds my actual email address as
> > > "Reply-To:" field. That's the common way to handle this on mailing
> > > lists,
> > > as also mentioned here:
> > > https://en.wikipedia.org/wiki/DMARC#From:_rewriting
> > > 
> > > So IMO patchew should automatically use the value of "Reply-To:" in that
> > > case as author of patches instead.
> > > 
> > > Reducing security cannot be the solution.
> > 
> > No, there's no need to reduce security.  Just change your local git
> > configuration to produce a 'From:' line in the commit body..
> 
> Got it. :)
> 
> > >> How are you sending patches ? With git send-email ? If so, maybe you
> > >> can
> > >> pass something like --from='"Christian Schoenebeck"
> > >> <qemu_oss@crudebyte.com>'. Since this is a different string, git will
> > >> assume you're sending someone else's patch : it will automatically add
> > >> an
> > >> extra From: made out of the commit Author as recorded in the git tree.
> > 
> > I think it is probably as simple as a 'git config' command to tell git
> > to always put a 'From:' in the body of self-authored patches when using
> > git format-patch; however, as I don't suffer from munged emails, I
> > haven't actually tested what that setting would be.

Well, I tried that Eric. The expected solution would be enabling this git 
setting:

git config [--global] format.from true
https://git-scm.com/docs/git-config#Documentation/git-config.txt-formatfrom

But as you can already read from the manual, the overall behaviour of git 
regarding a separate "From:" line in the email body was intended solely for 
the use case sender != author. So in practice (at least in my git version) git 
always makes a raw string comparison between sender (name and email) string 
and author string and only adds the separate From: line to the body if they 
differ.

Hence also "git format-patch --from=" only works here if you use a different 
author string (name and email) there, otherwise on a perfect string match it 
is simply ignored and you end up with only one "From:" in the email header.

So eventually I added one extra character in my name for now and removed it 
manually in the dumped emails subsequently (see today's
"[PATCH v7 0/3] 9p: Fix file ID collisions").

Besides that direct string comparison restriction; git also seems to have a 
bug here. Because even if you have sender != author, then git falsely uses 
author as sender of the cover letter, whereas the emails of the individual 
patches are encoded correctly.

Best regards,
Christian Schoenebeck