gpg: New option --import-filter

* g10/gpg.c (oImportFilter): New.
(opts): Add --import-filter.
(main): Handle option.
* g10/import.c: Include recsel.h, init.h, and mbox-util.h.
(import_keep_uid): New global var.
(cleanup_import_globals): New.
(parse_and_set_import_filter): New.
(filter_getval): New.
(apply_keep_uid_filter): New.
(import_one): Apply filter if set.
--

Funny new option.  It can for example be used to export a key with
only one user id:

  gpg --no-options --import --import-options import-export \
      --import-filter keep-uid='mbox=wk@gnupg.org'         \
     < full-key.pub > key-with-one-uid.pub

More features will eventually be added.

Signed-off-by: Werner Koch <wk@gnupg.org>

g10/gpg.c

@@ -300,6 +300,7 @@ enum cmd_and_opt_values
     oKeyServer,
     oKeyServerOptions,
     oImportOptions,
+    oImportFilter,
     oExportOptions,
     oListOptions,
     oVerifyOptions,
@@ -572,6 +573,7 @@ static ARGPARSE_OPTS opts[] = {
   ARGPARSE_s_s (oKeyServer, "keyserver", "@"),
   ARGPARSE_s_s (oKeyServerOptions, "keyserver-options", "@"),
   ARGPARSE_s_s (oImportOptions, "import-options", "@"),
+  ARGPARSE_s_s (oImportFilter,  "import-filter", "@"),
   ARGPARSE_s_s (oExportOptions, "export-options", "@"),
   ARGPARSE_s_s (oListOptions,   "list-options", "@"),
   ARGPARSE_s_s (oVerifyOptions, "verify-options", "@"),
@@ -2033,6 +2035,7 @@ parse_tofu_db_format (const char *db_format)
     }
 }
 
+
 /* This function called to initialized a new control object.  It is
    assumed that this object has been zeroed out before calling this
    function. */
@@ -3031,6 +3034,11 @@ main (int argc, char **argv)
 		  log_error(_("invalid import options\n"));
 	      }
 	    break;
+	  case oImportFilter:
+	    rc = parse_and_set_import_filter (pargs.r.ret_str);
+	    if (rc)
+              log_error (_("invalid filter option: %s\n"), gpg_strerror (rc));
+	    break;
 	  case oExportOptions:
 	    if(!parse_export_options(pargs.r.ret_str,&opt.export_options,1))
 	      {