cpp: Update key with --with-secret instead of updating it twice

* lang/cpp/src/key.cpp (Key::update): Call Context::key() only once
with KeyListMode::WithSecret.
--

With gpg >= 2.1, get the key with --with-secret instead of first trying
to get the secret key and, if that fails, getting the public key.

GnuPG-bug-id: 4794

lang/cpp/src/key.cpp

@@ -29,6 +29,7 @@
 #include "util.h"
 #include "tofuinfo.h"
 #include "context.h"
+#include "engineinfo.h"
 
 #include <gpgme.h>
 
@@ -363,19 +364,24 @@ void Key::update()
                         KeyListMode::SignatureNotations |
                         KeyListMode::Validate |
                         KeyListMode::WithTofu |
-                        KeyListMode::WithKeygrip);
+                        KeyListMode::WithKeygrip |
+                        KeyListMode::WithSecret);
     Error err;
-    auto newKey = ctx->key(primaryFingerprint(), err, true);
+    Key newKey;
+    if (GpgME::engineInfo(GpgME::GpgEngine).engineVersion() < "2.1.0") {
+        newKey = ctx->key(primaryFingerprint(), err, true);
         // Not secret so we get the information from the pubring.
         if (newKey.isNull()) {
             newKey = ctx->key(primaryFingerprint(), err, false);
         }
+    } else {
+        newKey = ctx->key(primaryFingerprint(), err, false);
+    }
     delete ctx;
     if (err) {
         return;
     }
     swap(newKey);
-    return;
 }
 
 // static