Implement diff for unsaved changes

Task-number: QTCREATORBUG-9732
Change-Id: I7e0f1d18046451ac1bc84b8c28113d72f63642a8
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/diffeditor/diffeditorplugin.h

@@ -27,8 +27,13 @@
 
 #include "diffeditor_global.h"
 
+#include <texteditor/textdocument.h>
 #include <extensionsystem/iplugin.h>
 
+QT_FORWARD_DECLARE_CLASS(QAction)
+
+namespace Core { class IEditor; }
+
 namespace DiffEditor {
 namespace Internal {
 
@@ -42,7 +47,11 @@ public:
     void extensionsInitialized();
 
 private slots:
-    void diff();
+    void updateCurrentEditor(Core::IEditor *editor);
+    void updateActions();
+    void diffCurrentFile();
+    void diffAllModifiedFiles();
+    void diffExternalFiles();
 
 #ifdef WITH_TESTS
     void testMakePatch_data();
@@ -50,6 +59,9 @@ private slots:
     void testReadPatch_data();
     void testReadPatch();
 #endif // WITH_TESTS
+private:
+    QAction *m_diffCurrentFileAction;
+    QPointer<TextEditor::TextDocument> m_currentTextDocument;
 };
 
 } // namespace Internal