qt: Add factory function for secret subkey export job

* lang/qt/src/protocol.h (class Protocol): Add member function
secretSubkeyExportJob.
* lang/qt/src/protocol_p.h (Protocol::secretSubkeyExportJob): Implement.

* lang/qt/tests/run-exportjob.cpp (showUsageAndExitWithCode): Print
new option.
(createExportJob): Create secret subkey export job if requested.
(main): New option --secret-subkey.
--

GnuPG-bug-id: 5757

lang/qt/src/protocol.h

@@ -128,6 +128,7 @@ public:
     virtual ExportJob            *publicKeyExportJob(bool armor = false) const = 0;
     // the second parameter is ignored; the passphrase in the exported file is always utf-8 encoded
     virtual ExportJob            *secretKeyExportJob(bool armor = false, const QString & = QString()) const = 0;
+    virtual ExportJob            *secretSubkeyExportJob(bool armor = false) const = 0;
     virtual DownloadJob          *downloadJob(bool armor = false) const = 0;
     virtual DeleteJob            *deleteJob() const = 0;
     virtual SignEncryptJob       *signEncryptJob(bool armor = false, bool textMode = false) const = 0;

lang/qt/src/protocol_p.h

@@ -254,6 +254,17 @@ public:
         return new QGpgME::QGpgMEExportJob(context, GpgME::Context::ExportSecret);
     }
 
+    QGpgME::ExportJob *secretSubkeyExportJob(bool armor) const Q_DECL_OVERRIDE
+    {
+        GpgME::Context *context = GpgME::Context::createForProtocol(mProtocol);
+        if (!context) {
+            return nullptr;
+        }
+
+        context->setArmor(armor);
+        return new QGpgME::QGpgMEExportJob(context, GpgME::Context::ExportSecretSubkey);
+    }
+
     QGpgME::RefreshKeysJob *refreshKeysJob() const Q_DECL_OVERRIDE
     {
         if (mProtocol != GpgME::CMS) { // fixme: add support for gpg, too

lang/qt/tests/run-exportjob.cpp

@@ -52,13 +52,16 @@ static void showUsageAndExitWithCode(int exitCode)
     cerr << "Usage: run-exportjob [OPTION]... [PATTERN]...\n"
          "Options:\n"
          "  --secret         export secret keys instead of public keys\n"
+         "  --secret-subkey  export secret subkeys instead of public keys\n";
 
     exit(exitCode);
 }
 
 static auto createExportJob(unsigned int mode)
 {
-    if (mode & Context::ExportSecret) {
+    if (mode & Context::ExportSecretSubkey) {
+        return QGpgME::openpgp()->secretSubkeyExportJob(/*armor=*/true);
+    } else if (mode & Context::ExportSecret) {
         return QGpgME::openpgp()->secretKeyExportJob(/*armor=*/true);
     }
     return QGpgME::openpgp()->publicKeyExportJob(/*armor=*/true);
@@ -90,6 +93,9 @@ int main(int argc, char *argv[])
         } else if (arg == QLatin1String{"--secret"}) {
             exportMode = Context::ExportSecret;
             arguments.pop_front();
+        } else if (arg == QLatin1String{"--secret-subkey"}) {
+            exportMode = Context::ExportSecretSubkey;
+            arguments.pop_front();
         } else {
             cerr << "Error: Invalid option " << arg.toStdString() << std::endl;
             showUsageAndExitWithCode(1);