VcsManager: Simplify usage of clearVersionControlCache

Change-Id: Iaf2f65da31a33979c30e63c29a706a568cc5fd1c
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/clearcase/clearcaseplugin.cpp

@@ -2315,7 +2315,7 @@ public:
         m_editor(0)
     {
         ClearCasePlugin::instance()->setFakeCleartool(true);
-        VcsManager::instance()->clearVersionControlCache();
+        VcsManager::clearVersionControlCache();
 
         FileSaver srcSaver(fileName);
         srcSaver.write(QByteArray());

src/plugins/coreplugin/iversioncontrol.cpp

@@ -140,21 +140,21 @@ namespace Core {
 
 TestVersionControl::~TestVersionControl()
 {
-    VcsManager::instance()->clearVersionControlCache();
+    VcsManager::clearVersionControlCache();
 }
 
 void TestVersionControl::setManagedDirectories(const QHash<QString, QString> &dirs)
 {
     m_managedDirs = dirs;
     m_dirCount = 0;
-    VcsManager::instance()->clearVersionControlCache();
+    VcsManager::clearVersionControlCache();
 }
 
 void TestVersionControl::setManagedFiles(const QSet<QString> &files)
 {
     m_managedFiles = files;
     m_fileCount = 0;
-    VcsManager::instance()->clearVersionControlCache();
+    VcsManager::clearVersionControlCache();
 }
 
 bool TestVersionControl::managesDirectory(const QString &filename, QString *topLevel) const

src/plugins/coreplugin/vcsmanager.h

@@ -92,13 +92,12 @@ public:
      */
     static QStringList additionalToolsPath();
 
+    static void clearVersionControlCache();
+
 signals:
     void repositoryChanged(const QString &repository);
     void configurationChanged(const IVersionControl *vcs);
 
-public slots:
-    static void clearVersionControlCache();
-
 private:
     explicit VcsManager(QObject *parent = 0);
     ~VcsManager();

src/plugins/vcsbase/commonsettingspage.cpp

@@ -61,7 +61,7 @@ CommonSettingsWidget::CommonSettingsWidget(QWidget *parent) :
     connect(Core::VcsManager::instance(), &Core::VcsManager::configurationChanged,
             this, &CommonSettingsWidget::updatePath);
     connect(m_ui->cacheResetButton, &QPushButton::clicked,
-            this, [] { Core::VcsManager::clearVersionControlCache(); });
+            Core::VcsManager::instance(), &Core::VcsManager::clearVersionControlCache);
 }
 
 CommonSettingsWidget::~CommonSettingsWidget()