Re: [PATCH] format-patch: fix ignored encode_email_headers for cover letter

[Simon Ser <contact@emersion.fr>]

On Thursday, November 9th, 2023 at 19:35, Jeff King <peff@peff.net> wrote:

> That makes sense, and your patch looks the right thing to do as an
> immediate fix. But I have to wonder:
> 
>   1. Are there other bits that need to be copied? Grepping for other
>      code that does the same thing, I see that show_log() and
>      cmd_format_patch() copy a lot more. (For that matter, why doesn't
>      make_cover_letter() just use the context set up by
>      cmd_format_patch()?).
> 
>   2. Why are we copying this stuff at all? When we introduced the
>      pretty-print context back in 6bf139440c (clean up calling
>      conventions for pretty.c functions, 2011-05-26), the idea was just
>      to keep all of the format options together. But later, 6d167fd7cc
>      (pretty: use fmt_output_email_subject(), 2017-03-01) added a
>      pointer to the rev_info directly. So could/should we just be using
>      pp->rev->encode_email_headers here?
> 
>      Or if that field is not always set (or we want to override some
>      elements), should there be a single helper function to initialize
>      the pretty_print_context from a rev_info, that could be shared
>      between spots like show_log() and make_cover_letter()?
> 
> I don't think that answering those questions needs to hold up your
> patch. We can take it as a quick fix for a real bug, and then anybody
> interested can dig further as a separate topic on top.

These are good questions indeed. Unfortunately I don't hink I'll have time to
work on this though.

> > +test_expect_success 'cover letter with --cover-from-description subject (UTF-8 subject line)' '
> > +	test_config branch.rebuild-1.description "Café?
> > +
> > +body" &&
> > +	git checkout rebuild-1 &&
> > +	git format-patch --stdout --cover-letter --cover-from-description subject --encode-email-headers main >actual &&
> > +	grep "^Subject: \[PATCH 0/2\] =?UTF-8?q?Caf=C3=A9=3F?=$" actual &&
> > +	! grep "Café" actual
> > +'
> 
> The test looks correct to me.
> 
> Some of these long lines (and the in-string newlines!) make this ugly
> and hard to read. But it is also just copying the already-ugly style of
> nearby tests. So I'm OK with that. But a prettier version might be:
> 
>   test_expect_success 'cover letter respects --encode-email-headers' '
>         test_config branch.rebuild-1.description "Café?" &&
>         git checkout rebuild-1 &&
>         git format-patch --stdout --encode-email-headers \
>                 --cover-letter --cover-from-description=subject \
>                 main >actual &&
>         ...
>   '

Yeah, that sounds better indeed. Let me know if you want me to resend a cleaner
version of the test.

> I also wondered if we could be just be testing this much more easily
> with another header like "--to". But I guess that would be found in both
> the cover letter and the actual patches (we also don't seem to encode
> it even in the regular patches; is that a bug?).

That sounds like another bug indeed… But maybe that'll be harder to fix. To
Q-encode this field one needs to split off the full name and actual mail
address ("André <andre@example.org>" would be split into "André" and
"andre@example.org"), then Q-encode the full name, then join the strings
together again. In particular, it's incorrect to Q-encode the full string.