Pinentry curses fallback for gpg

[John Lane]

Hello, I am trying to work out a few things with GnuPG that aren't clear
to me after reading the available documentation. I hope it's ok to ask
for some help?

Here's my first problem:

I cannot work our how to tell my desktop-less system to use the curses
pinentry program. I can see that is is configurable for gpg-agent.conf
but I see no equivalent for gpg.conf. The only way I have been able to
do this is to re-point a symlink /usr/bin/pinentry to point to
/usr/bin/pinentry-curses instead of /usr/bin/pinentry-gtk.

I have read the pinentry readme and see the configure options for it. I
have cross checked with how the package is built for Arch Linux, which
is the Linux distribution that I use. The configure options are

 ./configure --prefix=/usr \
        --enable-pinentry-curses \
        --disable-pinentry-gtk \
        --disable-pinentry-qt \
        --enable-pinentry-gtk2 \
        --enable-pinentry-qt4 \
        --enable-fallback-curses

The installed binaries are like this:

lrwxrwxrwx 1 root root     14 May  6  2013 /usr/bin/pinentry ->
/usr/bin/pinentry-gtk2
-rwxr-xr-x 1 root root  48216 May  6  2013 /usr/bin/pinentry-curses
-rwxr-xr-x 1 root root 107384 May  6  2013 /usr/bin/pinentry-gtk-2
-rwxr-xr-x 1 root root 153064 May  6  2013 /usr/bin/pinentry-qt4

It isn't possible to launch the gtk-2 or qt4 versions without the
requisite libraries being installed, so both fail rather than fall back
to the curses version:

# /usr/bin/pinentry-qt4
/usr/bin/pinentry-qt4: error while loading shared libraries:
libQtCore.so.4: cannot open shared object file: No such file or directory

# /usr/bin/pinentry-gtk-2
/usr/bin/pinentry-gtk-2: error while loading shared libraries:
libgtk-x11-2.0.so.0: cannot open shared object file: No such file or
directory

The curses version works fine. Now, as far as I understand, the gnupg
binary uses the symlink "/usr/bin/pinentry" and, with the above
configuration that means the gtk2 version. And, if the system doesn't
have that installed then it fails.

I can obviously change the symlink to point to the curses version but,
if I do, it'll eventually get reset by my distributions package manager.

As far as I can tell, it's the pinentry package's "make install" that
creates this symlink rather than something distribution-specific.

So, what is the correct, approved way to get gpg to use the curses
pinentry ?

Thanks.