bug#24350: 24.5; epg: unsupported cpr_get keywords incorrectly handled

[Neal H . Walfield]

Hi,

When GnuPG needs input, it sometimes uses cpr_get (in
gnupg/g10/cpr.c:cpr_get).  When this occurs, epg shows the prompt's
keyword.  The correct thing to do if epg does not support the keyword is
to send a carriage return to GnuPG to accept the default.  (Of course,
it is better to actually support the keywords, but this is a separate
issue.)

It is possible to reproduce this using the new tofu trust model in
GnuPG, which epg does not yet support.  Specifically:

 1. Set the trust-model to tofu+pgp in gpg.conf:

    trust-model tofu+pgp

 2. Run M-x epa-encrypt-region in emacs.

 3. Select a key for which there is another key with the same email
     address.

 4. In the mini buffer, emacs will show "tofu.conflict:" and wait for
    input.

Thanks!

:) Neal

In GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2016-04-08 on binet, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11604000
System Description:     Debian GNU/Linux 8.5 (jessie)

Configured using:
 `configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
 --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
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 'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
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Important settings:
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Major mode: Folder

Minor modes in effect:
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Making thread...done
Updating thread indent...done
Updating marks...
Scoring...done
Updated (-0/+2) message(s).
Updated (-0/+2) message(s)
Retrieving...done
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/usr/share/emacs24/site-lisp/flim/sasl hides /usr/share/emacs/24.5/lisp/net/sasl
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/usr/share/emacs24/site-lisp/flim/hmac-md5 hides 
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/usr/share/emacs24/site-lisp/flim/ntlm hides /usr/share/emacs/24.5/lisp/net/ntlm
/usr/share/emacs24/site-lisp/flim/sasl-digest hides 
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/usr/share/emacs/site-lisp/wl/utils/rfc2368 hides 
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/usr/share/emacs24/site-lisp/mailcrypt/mc-pgp5 hides 
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/usr/share/emacs24/site-lisp/mailcrypt/mc-setversion hides 
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/usr/share/emacs24/site-lisp/mailcrypt/expect hides 
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/usr/share/emacs24/site-lisp/mailcrypt/mc-gpg hides 
/usr/share/emacs/site-lisp/mailcrypt/mc-gpg
/usr/share/emacs24/site-lisp/mailcrypt/mailcrypt hides 
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Memory information:
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