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

[Herbert Valerio Riedel <hvr@gnu.org>]

>> The end result is that `notmuch-message-headers` variable has no effect.

> Not sure if you are still interested, but this should be fixed in
> notmuch 0.35 (see show.extra_headers in notmuch-config(1)).

I just stumbled over this issue when trying to add "Message-Id" to the
list of shown messages as the docstring of the custom variable
definition in 'notmuch-show.el' didn't mention that I needed to tweak my
config or that only a small subset of headers might be supported:

--8<---------------cut here---------------start------------->8---
(defcustom notmuch-message-headers '("Subject" "To" "Cc" "Date")
  "Headers that should be shown in a message, in this order.

For an open message, all of these headers will be made visible
according to `notmuch-message-headers-visible' or can be toggled
with `notmuch-show-toggle-visibility-headers'. For a closed message,
only the first header in the list will be visible."
  :type '(repeat string)
  :group 'notmuch-show)
--8<---------------cut here---------------end--------------->8---

I suggest adding a hint there that tweaking 'show.extra_headers' might
be necessary.