git format.from (was: 9p: Fix file ID collisions)

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Dienstag, 24. September 2019 00:24:15 CEST Jeff King wrote:
> > On the other hand, considering the already existing --from argument and
> > "format.from" config option:
> > https://git-scm.com/docs/git-config#Documentation/git-config.txt-formatfro
> > m
> > 
> > Wouldn't it make sense to just drop the currently existing sender !=
> > author
> > string comparison in git and simply always add the "From:" line to the
> > email's body if "format.from yes" is used, instead of introducing a
> > suggested 2nd (e.g. "always-from") option? I mean sure automatically
> > removing redundant information in the generated emails if sender ==
> > author sounds nice on first thought, but does it address anything useful
> > in practice to justify introduction of a 2nd related option?
> 
> Yes, the resulting mail would be correct, in the sense that it could be
> applied just fine by git-am. But I think it would be uglier. IOW, I
> consider the presence of the in-body From to be a clue that something
> interesting is going on (like forwarding somebody else's patch). So from
> my perspective, it would just be useless noise. Other communities may
> have different opinions, though (I think I have seen some kernel folks
> always including all of the possible in-body headers, including Date).
> But it seems like it makes sense to keep both possibilities.

Exactly, current git behaviour is solely "prettier" (at first thought only 
though), but does not address anything useful in real life.

Current git behaviour does cause real life problems though: Many email lists 
are munging emails of patch senders whose domain is configured for requiring 
domain's emails being DKIM signed and/or being subject to SPF rules (a.k.a 
DMARC). So original sender's From: header is then automatically replaced by an 
alias (by e.g. mailman): https://en.wikipedia.org/wiki/DMARC#From:_rewriting

For instance the email header:

From: "Bob Bold" <bold@foo.com>

is automatically replaced by lists by something like

From: "Bob Bold via Somelist" <somelist@gnu.org>

And since git currently always drops the From: line from the email's body if
sender == author, as a consequence maintainers applying patches from such 
lists, always need to rewrite git history subsequently and have to replace 
patch author's identity manually for each commit to have their correct, real 
email address and real name in git history instead of something like
"Bob Bold via Somelist" <somelist@gnu.org>

So what do you find "uglier"? I prefer key info not being lost as default 
behaviour. :-)

Best regards,
Christian Schoenebeck