VcsBase: Add a convenience function execBgCommand

Creates and executes a command asynchronously, passing its stdout to a
callback function.

Change-Id: I6be7e803fadf708ca7dc587b612a5a63e9bf09c3
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/vcsbase/vcsbaseclient.h

@@ -82,6 +82,11 @@ public:
                               VcsBaseEditorWidget *editor = nullptr,
                               JobOutputBindMode mode = NoOutputBind) const;
 
+    VcsCommand *execBgCommand(const Utils::FilePath &workingDirectory,
+                              const QStringList &args,
+                              const std::function<void (const QString &)> &outputCallback,
+                              unsigned flags = 0) const;
+
     void enqueueJob(VcsCommand *cmd, const QStringList &args,
                     const Utils::ExitCodeInterpreter &interpreter = {}) const;