emacs: Wrong "From" address when forwarding a mail

[Jinwoo Lee <jinwoo68@gmail.com>]

I have two accounts set up in my notmuch configuration.  And when I'm
forwarding a mail using notmuch-show-forward-message, it always uses my
primary account as its From address no matter which account that
original mail has been delivered to.

For example:
1. I got a mail delivered to my personal address, personal@somemail.com,
   which is my secondary account.
2. I want to forward the mail to someone else and I press 'f' for
   notmuch-show-forward-message.
3. It always uses my corp address, corp@somecompany.com, which is my
   primary account, as the From address, instead of
   personal@somemail.com.

This is quite annoying and has some privacy issues because my corporate
account may be scanned by my employer.  I'm working around this by doing
'C-u f', which allows me to choose the From address, but it's very easy
to just press 'f' and make a mistake.

Can we make notmuch-show-forward-message behave like
notmuch-show-reply-sender, which chooses the From address correctly?

Thanks,
-jinwoo