VCS: Simplify promptSubmit a bit more

+ fix regression for Git, which allowed to commit invalid commits.

Amends commit 9b61e484be.

Change-Id: I7571863bb982bfae1aa040e08f8c68010b14b147
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/vcsbase/vcsbaseplugin.h

@@ -137,6 +137,8 @@ public:
     virtual QString commitDisplayName() const;
 
     void commitFromEditor();
+    virtual bool canCommitOnFailure() const { return true; }
+    bool submitActionTriggered() const { return m_submitActionTriggered; }
 
 protected:
     // Prompt to save all files before commit: