[BUG] Custom headers in `notmuch-message-headers` are broken

[David Bremner]

Jan Malakhovski <oxij at oxij.org> writes:

>
> internally. The latter produces a sexp with
>
> ```
> :headers (:Subject "" :From "" :To "" :Reply-To "" :Date "")
> ```
>
> even when the message has many more headers.

Yes, you are correct that currently format_headers_sprinter in
notmuch-show.c only outputs a fixed set of headers.  Unlike indexing new
headers, I don't think there's any hidden complexity here, if someone is
looking for a project.

d