Git: Add Sign off feature in git commit view

Change-Id: Icb0a8818f707d6a874a9b97318fc6a93205b4ce9
Signed-off-by: Tasuku Suzuki <tasuku.suzuki@qt.io>
Reviewed-by: André Hartmann <aha_1980@gmx.de>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/git/commitdata.h

@@ -60,6 +60,7 @@ public:
     QString email;
     bool bypassHooks;
     PushAction pushAction;
+    bool signOff;
 };
 
 enum FileState {