gpg: New option --use-only-openpgp-card

* g10/gpg.c (opts): Add option.
(main): Set flag.
* g10/options.h: Add flags.use_only_openpgp_card.
* g10/call-agent.c (start_agent): Implement option.
--

With the previous patch we switch to autoselect an application
instead of requesting an openpgp card.  This option allows to revert
this in case of use use cases which expected the former behaviour.

Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit c185f6dfbd1bfd809369da789239a371e9d1610e)
This was first added to the 2.2 branch.

doc/gpg.texi

@@ -3516,6 +3516,13 @@ file and returns with failure if the configuration file would prevent
 @command{@gpgname} from startup.  Thus it may be used to run a syntax check
 on the configuration file.
 
+@c @item --use-only-openpgp-card
+@c @opindex use-only-openpgp-card
+@c Only access OpenPGP card's and no other cards.  This is a hidden
+@c option which could be used in case an old use case required the
+@c OpenPGP card while several cards are avaiable.  This option might be
+@c removed if it turns out that nobody requires it.
+
 @end table
 
 @c *******************************

g10/call-agent.c

@@ -367,7 +367,9 @@ start_agent (ctrl_t ctrl, int flag_for_card)
       if (!(flag_for_card & FLAG_FOR_CARD_SUPPRESS_ERRORS))
         rc = warn_version_mismatch (agent_ctx, SCDAEMON_NAME, 2);
       if (!rc)
-        rc = assuan_transact (agent_ctx, "SCD SERIALNO",
+        rc = assuan_transact (agent_ctx,
+                              opt.flags.use_only_openpgp_card?
+                              "SCD SERIALNO openpgp" : "SCD SERIALNO",
                               NULL, NULL, NULL, NULL,
                               learn_status_cb, &info);
       if (rc && !(flag_for_card & FLAG_FOR_CARD_SUPPRESS_ERRORS))

g10/gpg.c

@@ -426,6 +426,7 @@ enum cmd_and_opt_values
     oKeyOrigin,
     oRequestOrigin,
     oNoSymkeyCache,
+    oUseOnlyOpenPGPCard,
 
     oNoop
   };
@@ -896,6 +897,10 @@ static ARGPARSE_OPTS opts[] = {
   ARGPARSE_s_n (oNoAutostart, "no-autostart", "@"),
   ARGPARSE_s_n (oNoSymkeyCache, "no-symkey-cache", "@"),
 
+  /* Options which can be used in special circumstances. They are not
+   * published and we hope they are never required.  */
+  ARGPARSE_s_n (oUseOnlyOpenPGPCard, "use-only-openpgp-card", "@"),
+
   /* Dummy options with warnings.  */
   ARGPARSE_s_n (oUseAgent,      "use-agent", "@"),
   ARGPARSE_s_n (oNoUseAgent, "no-use-agent", "@"),
@@ -3642,6 +3647,10 @@ main (int argc, char **argv)
             opt.def_new_key_algo = pargs.r.ret_str;
             break;
 
+          case oUseOnlyOpenPGPCard:
+            opt.flags.use_only_openpgp_card = 1;
+            break;
+
 	  case oNoop: break;
 
 	  default:

g10/options.h

@@ -251,6 +251,9 @@ struct
     unsigned int rfc4880bis:1;
     /* Hack: --output is not given but OUTFILE was temporary set to "-".  */
     unsigned int dummy_outfile:1;
+    /* Force the use of the OpenPGP card and do not allow the use of
+     * another card.  */
+    unsigned int use_only_openpgp_card:1;
   } flags;
 
   /* Linked list of ways to find a key if the key isn't on the local