Git: Offer creating remote branch if push fails due to the lack of it

If git push fails because the remote branch does not exists a dialog
will be shown which will allow the creation of the remote branch without
leaving the IDE (by executing the git push --set-upstream .. command
suggested by the git itself).

Fixes: QTCREATORBUG-21154
Change-Id: Id785fdc64e27865fba2255eafd2043367a5835ea
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/git/gitclient.h

@@ -78,6 +78,11 @@ enum StashFlag {
     NoPrompt       = 0x02
 };
 
+enum PushFailure {
+    NonFastForward,
+    NoRemoteBranch
+};
+
 class SubmoduleData
 {
 public:
@@ -381,6 +386,7 @@ private:
 
     QString m_gitQtcEditor;
     QMap<QString, StashInfo> m_stashInfo;
+    QString m_pushFallbackCommand;
     QStringList m_updatedSubmodules;
     bool m_disableEditor;
     QFutureSynchronizer<void> m_synchronizer; // for commit updates