Clarify GnuPG version compatibility chapter

* doc/misc/epa.texi (GnuPG version compatibility): Make the gpg-agent
description a bit clearer.
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Daiki Ueno 2016-02-22 10:40:42 +09:00
parent 5e34c3671a
commit 2667b3ebae

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@ -441,26 +441,30 @@ The default value is @code{t}.
@chapter GnuPG version compatibility
As of February 2016, there are three active branches of GnuPG: 2.1,
2.0, and 1.4. All those branches should work flawlessly with Emacs,
2.0, and 1.4. All those branches should work flawlessly with Emacs
with basic use-cases. They have, however, some incompatible
characteristics, which might be visible when used from Emacs.
@itemize
@item
The key store format used by 2.1 is incompatible with 1.4. That
means, a key created with 2.1 might not be visible with 1.4.
The key store format used by GnuPG 2.1 is incompatible with 1.4. That
means, a key created with GnuPG 2.1 is not visible with 1.4.
@item
2.1 uses a fixed Unix domain socket for gpg-agent, and ignores the
@code{GPG_AGENT_INFO} environment variable, used by 2.0 and 1.4.
GnuPG 2.1 uses a fixed address for the Unix domain socket used to
communicate with gpg-agent. The @code{GPG_AGENT_INFO} environment
variable, which is used by GnuPG 2.0 and 1.4, is ignored. That means,
if your system has both GnuPG 2.1 and 1.4, the gpg command from GnuPG
1.4 is not able to use gpg-agent provided by 2.1 (at least out of box).q
@item
2.1 (2.1.5 or later) has a mechanism to direct the Pinentry password
prompt to the Emacs minibuffer@footnote{To enable this feature, add
@samp{allow-emacs-pinentry} to @file{~/.gnupg/gpg-agent.conf} and let
gpg-agent reload the configuration, with: @samp{gpgconf --reload gpg-agent}},
which would be useful when you use Emacs remotely or from a text-only
terminal. That feature is not available in other versions, and more
GnuPG 2.1 (2.1.5 or later) has a mechanism to direct the Pinentry
password prompt to the Emacs minibuffer@footnote{To enable this
feature, add @samp{allow-emacs-pinentry} to
@file{~/.gnupg/gpg-agent.conf} and let gpg-agent reload the
configuration, with: @samp{gpgconf --reload gpg-agent}}, which would
be useful when you use Emacs remotely or from a text-only terminal.
That feature is not available in other versions, and more
specifically, with 2.0 (as of 2.0.29), there is no way to avoid the
graphical prompt.
@end itemize