add command line option to forcing reuse of existing process for debugging

src/Application.cpp

@@ -72,7 +72,10 @@ void Application::populateCommandLineParser(QCommandLineParser *parser)
         {{QStringLiteral("p")}, i18nc("@info:shell", "Change the value of a profile property."), QStringLiteral("property=value")},
         {{QStringLiteral("e")},
          i18nc("@info:shell", "Command to execute. This option will catch all following arguments, so use it as the last option."),
-         QStringLiteral("cmd")}};
+         QStringLiteral("cmd")},
+        {{QStringLiteral("force-reuse")}, i18nc("@info:shell", "Force re-using the existing instance even if it breaks functionality, e. g. --new-tab. Mostly for debugging.")},
+    };
+
     for (const auto &option : options) {
         parser->addOption(option);
     }

src/main.cpp

@@ -260,6 +260,10 @@ bool shouldUseNewProcess(int argc, char *argv[])
         arguments.append(QString::fromLocal8Bit(argv[i]));
     }
 
+    if (arguments.contains(QLatin1String("--force-reuse"))) {
+        return false;
+    }
+
     // take Qt options into consideration
     QStringList qtProblematicOptions;
     qtProblematicOptions << QStringLiteral("--session") << QStringLiteral("--name") << QStringLiteral("--reverse") << QStringLiteral("--stylesheet")