carry over headers into reply

[Eric Abrahamsen <eric@ericabrahamsen.net>]

I've been trying for a while to figure out how to draw the value of a
custom header from an edited mail message (the header inserted via
another function) and insert it into a reply to that message. I can't
seem to find any hooks (or even efficient places to advise functions)
that will let me slurp a header value from the original message, and
then place it in the reply that's being composed.

I've considered `message-fetch-reply-field' (which seemed promising),
and a custom `message-reply-to-function', and also advising
`message-get-reply-headers', but everything seems to only let me carry
over To and Cc headers from the original, not arbitrary headers.

I can always kludge it with some global variable and two advice forms,
but I'd much rather find something more graceful.

Is there anywhere where either advice or a hook can use
`message-fetch-reply-field' to get fields from the original, while
operating in the reply buffer?

If anyone who knows this code has a word of advice, I would love to hear
it!

Thanks,
Eric

-- 
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 of 2012-06-01 on pellet
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