VCS: Introduce Base class for VCS plugins, use in git.

Fixes:
- Cannot diff a file that does not belong to a project
- Cannot commit when a temporary diff/log view is open
  due to the current file pointing to a temporary directory
- git's project-related actions not passing the correct
  relative path.

Implementation:
- Centralize code to listen for Qt Creator's relevant state changes
  in VCSBasePlugin, dispatching the changes to the instances affected.
  (avoiding multiple invocations of searches/QFileInfo on current).
- Do the same for the corelistener catching closing SubmitEditors.
- Introduce VCSBasePluginState representing the relevant state
  (current file/project).
- Call git with working directory set and relative arguments
- Remove setEnabled/isEnabled() logic of IVersionControl
- Pass toplevel from VCSManager to avoid duplicate searches.

src/plugins/subversion/subversionplugin.h

@@ -32,8 +32,7 @@
 
 #include "subversionsettings.h"
 
-#include <coreplugin/icorelistener.h>
-#include <extensionsystem/iplugin.h>
+#include <vcsbase/vcsbaseplugin.h>
 
 QT_BEGIN_NAMESPACE
 class QDir;
@@ -43,6 +42,7 @@ QT_END_NAMESPACE
 
 namespace Core {
     class IVersionControl;
+    class IEditor;
 }
 namespace Utils {
     class ParameterAction;
@@ -52,6 +52,10 @@ namespace ProjectExplorer {
     class ProjectExplorerPlugin;
 }
 
+namespace VCSBase {
+    class VCSBaseSubmitEditor;
+}
+
 namespace Subversion {
 namespace Internal {
 
@@ -67,7 +71,7 @@ struct SubversionResponse
     QString message;
 };
 
-class SubversionPlugin : public ExtensionSystem::IPlugin
+class SubversionPlugin : public VCSBase::VCSBasePlugin
 {
     Q_OBJECT
 
@@ -77,7 +81,6 @@ public:
 
     bool initialize(const QStringList &arguments, QString *error_message);
     void extensionsInitialized();
-    bool editorAboutToClose(Core::IEditor *editor);
 
     void svnDiff(const QStringList &files, QString diffname = QString());
 
@@ -95,7 +98,6 @@ public:
     static SubversionPlugin *subversionPluginInstance();
 
 private slots:
-    void updateActions();
     void addCurrentFile();
     void deleteCurrentFile();
     void revertCurrentFile();
@@ -112,6 +114,10 @@ private slots:
     void submitCurrentLog();
     void diffFiles(const QStringList &);
 
+protected:
+    virtual void updateActions(VCSBase::VCSBasePlugin::ActionState);
+    virtual bool submitEditorAboutToClose(VCSBase::VCSBaseSubmitEditor *submitEditor);
+
 private:
     inline bool isCommitEditorOpen() const;
     QString currentFileName() const;
@@ -128,11 +134,11 @@ private:
     void startCommit(const QStringList &files);
     bool commit(const QString &messageFile, const QStringList &subVersionFileList);
     void cleanCommitMessageFile();
+    inline SubversionControl *subVersionControl() const;
 
     const QStringList m_svnDirectories;
 
     SubversionSettings m_settings;
-    SubversionControl *m_versionControl;
     QString m_commitMessageFileName;
 
     ProjectExplorer::ProjectExplorerPlugin *m_projectExplorer;
@@ -154,32 +160,12 @@ private:
     QAction *m_submitDiffAction;
     QAction *m_submitUndoAction;
     QAction *m_submitRedoAction;
+    QAction *m_menuAction;
     bool    m_submitActionTriggered;
 
     static SubversionPlugin *m_subversionPluginInstance;
 };
 
-// Just a proxy for SubversionPlugin
-class CoreListener : public Core::ICoreListener
-{
-    Q_OBJECT
-public:
-    CoreListener(SubversionPlugin *plugin) : m_plugin(plugin) { }
-
-    // Start commit when submit editor closes
-    bool editorAboutToClose(Core::IEditor *editor) {
-        return m_plugin->editorAboutToClose(editor);
-    }
-
-    // TODO: how to handle that ???
-    bool coreAboutToClose() {
-        return true;
-    }
-
-private:
-    SubversionPlugin *m_plugin;
-};
-
 } // namespace Subversion
 } // namespace Internal