Re: git-send-email: Send with mutt(1)

From: Jeff King <peff@peff.net>
Date: Nov 7, 2023, 20:16 UTC
Message-ID: <20231107201655.GA507701@coredump.intra.peff.net>
In-Reply-To: <ZUqDwnmu9d1dD1tb@devuan>

On Tue, Nov 07, 2023 at 07:36:44PM +0100, Alejandro Colomar wrote:

Show 11 quoted lines

> > I assume what you want out of send-email here is the actual generation
> > of patch emails. But under the hood that is all done by git-format-patch
> > anyway. So for example if you do:
> 
> Yeah, most of it is done by format-patch.  There are few things I
> actually need from send-email.  One of them is generating the Cc from
> the sign-offs and other tags found in the patch.
> 
> I had been thinking these days that it would be useful to have
> format-patch generate those.  How about adding a --signed-off-by-cc to
> format-patch?

That seems like a reasonable feature. Probably it should be --cc-from-trailer=signed-off-by, and then you could do the same with other trailers.

It feels like you could _almost_ do it with the existing --format='%(trailers)' functionality, but there's no way to say "do the regular --format=email output, but also stick this extra format in the headers section". Plus there are probably some niceties you'd get from Git knowing that you're adding headers (like de-duping addresses).

That feature might end up somewhat hairy, though, as then you get into questions of parsing address lists, etc. We do all that now in perl with send-email, where we can lean on some parsing libraries. So I dunno.

Show 8 quoted lines

> > If you're sending a long series, it's helpful to pre-populate various
> > headers in the format-patch command with "--to", etc. I usually do so by
> > sending the cover letter directly via mutt, and then using some perl
> > hackery to convert those headers into format-patch args. The script I
> 
> Indeed, that hackery is what send-email already does, so how about
> moving those features a bit upstream so that format-patch can do them
> too?

Yeah, if they existed in format-patch I might be able to reuse them. I am hesitant, though, just because handling all the corner cases on parsing is going to be a bit of new C code.

> Although then, maybe it's simpler to teach send-email to learn to use
> mutt(1) under the hood for the actual send.

I think you will find some corner cases in trying to make mutt act just like an mta accepting delivery. Two I can think of:

  1. It will take a body on stdin, but not a whole message. We can hack
     around that with some postponed-folder magic, though.

  2. Bcc headers are stripped before sendmail sees the message (but
     those addresses appear on the command-line). Converting that back
     to bcc so that mutt can then re-strip them would be annoying but
     possible. If you don't use bcc, it probably makes sense to just
     punt on this.

So maybe a script like this:

-- >8 -- #!/bin/sh

# ignore arguments; mutt will parse them itself # from to/cc headers. Note that we'll miss bcc this # way, but handling that would probably be kind of # tricky; we'd need to re-add those recipients as actual # bcc headers so that mutt knows how to handle them.

# spool the message to a fake mbox; we need to add
# a "From" line to make it look legit
trap 'rm -f to-send' 0 &&
{
  echo "From whatever Mon Sep 17 00:00:00 2001" &&
  cat
} >to-send &&

# and then have mutt "resume" it. We have to redirect
# stdin back from the terminal, since ours is a pipe
# with the message contents.
mutt -p \
  -e 'set postponed=to-send' \
  -e 'set edit_headers=yes' \
  </dev/tty
-- 8< --

and then in your git config:

  [sendemail]
  sendmailcmd = /path/to/mutt-as-mta.sh

There are mutt-specific bits there that I don't think send-email should have to know about. Perhaps there are generic options that send-email could learn, but it really feels like you'd do better teaching mutt to be more ready to handle this (like taking a whole message on stdin, headers and all, rather than just a body).

-Peff