gnupg: Automatically fallback to 'always policy when non-interactive.

Previously to this change, the 'guix refresh' download
policy (--key-download)would default to 'interactive', which would throw a
backtrace when guix was invoked with its stdin not connected to a peusdo
terminal (tty).  This change makes the new default value 'auto' use
interactive only in an interactive environment, with 'always' used as
fallback.

* doc/guix.texi (Invoking guix refresh): Adjust doc.
* etc/completion/fish/guix.fish: Adjust accordingly.
* etc/completion/zsh/_guix (_guix_list_installed_packages): Likewise.
* guix/gnupg.scm (gnupg-verify*): Change default #:key-download argument value
to 'auto.  Update doc.  Validate argument.  Raise an error in case read-line
returns #<eof>.
* guix/import/gnu.scm (gnu-package->sexp): <#:key-download>: Change default
value to 'auto.
* guix/import/gnu.scm (gnu->guix-package): <#:key-download>: Likewise.
* guix/scripts/import/gnu.scm (%options): Add "auto" to accepted
--key-download values.
(%default-options): Set default key-download option to the 'auto value.
(show-help): Update doc.
* guix/scripts/refresh.scm (show-help): Update doc.
(update-package) <#:key-download>: Change default value to 'auto.  Update doc.
* guix/upstream.scm (download-tarball): <#:key-download>: Likewise.
(package-update): Likewise.

Change-Id: Id1ca8fd6d453ca4bc5b372534445e3beab9133a8
Fixes: https://issues.guix.gnu.org/76112
Reviewed-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 3 insertions, 3 deletions

diff --git a/etc/completion/fish/guix.fish b/etc/completion/fish/guix.fish
index e6c290256f2..9e3b3211ea1 100644
--- a/etc/completion/fish/guix.fish
+++ b/etc/completion/fish/guix.fish
@@ -284,7 +284,7 @@ complete -f -c guix -n '__fish_guix_using_command refresh' -l list-updaters -d '
 complete -f -c guix -n '__fish_guix_using_command refresh' -l list-dependent -d 'list top-level dependent packages that would need to be rebuilt as a result of upgrading PACKAGE'
 complete -f -c guix -n '__fish_guix_using_command refresh' -a "--key-server=" -d 'use HOST as the OpenPGP key server'
 complete -f -c guix -n '__fish_guix_using_command refresh' -a "--gpg=" -d 'use COMMAND as the GnuPG 2.x command'
-complete -f -c guix -n '__fish_guix_using_command refresh' -a "--key-download=" -d 'handle missing OpenPGP keys according to POLICY.' --exclusive --arguments "always never interactive"
+complete -f -c guix -n '__fish_guix_using_command refresh' -a "--key-download=" -d 'handle missing OpenPGP keys according to POLICY.' --exclusive --arguments "always auto never interactive"
 
 #### publish
 set -l remotecommands port= listen= user= compression ttl= repl
@@ -321,7 +321,7 @@ set -l remotecommands import gnu nix pypi cpan hackage elpa gem cran crate texli
 complete -f -c guix -n '__fish_guix_needs_command' -a import -d 'Run IMPORTER with ARGS'
 ##### import gnu
 complete -f -c guix -n '__fish_guix_using_command import; and not __fish_seen_subcommand_from $remotecommands' -a gnu -d 'Return a package declaration template for PACKAGE, a GNU package.'
-complete -f -c guix -n '__fish_guix_using_command import; and __fish_seen_subcommand_from gnu' -a "--key-download=" -d 'handle missing OpenPGP keys according to POLICY: "always", "never", and "interactive", which is also used when "key-download" is not specified.'
+complete -f -c guix -n '__fish_guix_using_command import; and __fish_seen_subcommand_from gnu' -a "--key-download=" -d 'handle missing OpenPGP keys according to POLICY: "always", "auto", "never", and "interactive", which is also used when "key-download" is not specified.'
 ##### import pypi
 complete -f -c guix -n '__fish_guix_using_command import; and not __fish_seen_subcommand_from $remotecommands' -a pypi -d 'Import and convert the PyPI package for PACKAGE-NAME.'
 ##### import cpan
diff --git a/etc/completion/zsh/_guix b/etc/completion/zsh/_guix
index 9b1f16c664e..42b92475a94 100644
--- a/etc/completion/zsh/_guix
+++ b/etc/completion/zsh/_guix
@@ -507,7 +507,7 @@ _guix_list_installed_packages()
         '--keyring=[use FILE as the keyring of upstream OpenPGP keys]:FILE:_files' \
         '--key-server=[use HOST as the OpenPGP key server]:HOST_hosts' \
         '--gpg=[use COMMAND as the GnuPG 2.x command]:COMMAND' \
-        '--key-download=[handle missing OpenPGP keys according to POLICY:]:POLICY:(always interactive never)' \
+        '--key-download=[handle missing OpenPGP keys according to POLICY:]:POLICY:(always auto interactive never)' \
         '--load-path=[prepend DIR to the package module search path]:DIR:_files -/' \
         {-V,--version}'[display version information and exit]' \
         '*:package:->packages'