VCS[git]: Add support for stashes.

Add non-modal stash management dialog and additional menu option
"Stash snapshot..." to stash away changes prompting for a description,
which will immediately replay the stash (take snapshot and continue
working).
Add interface to IVersionControl for creating/restoring/deleting
snapshots for backup/complex undo operations (currently supported
by git only). Add test options to VCSBasePlugin.
Clean up and extend git client accordingly.

src/plugins/cvs/cvscontrol.cpp

@@ -55,6 +55,7 @@ bool CVSControl::supportsOperation(Operation operation) const
         break;
     case OpenOperation:
     case CreateRepositoryOperation:
+    case SnapshotOperations:
         rc = false;
         break;
     }
@@ -84,6 +85,26 @@ bool CVSControl::vcsCreateRepository(const QString &)
     return false;
 }
 
+QString CVSControl::vcsCreateSnapshot(const QString &)
+{
+    return QString();
+}
+
+QStringList CVSControl::vcsSnapshots(const QString &)
+{
+    return QStringList();
+}
+
+bool CVSControl::vcsRestoreSnapshot(const QString &, const QString &)
+{
+    return false;
+}
+
+bool CVSControl::vcsRemoveSnapshot(const QString &, const QString &)
+{
+    return false;
+}
+
 bool CVSControl::managesDirectory(const QString &directory) const
 {
     return m_plugin->managesDirectory(directory);

src/plugins/cvs/cvscontrol.h

@@ -53,6 +53,10 @@ public:
     virtual bool vcsAdd(const QString &fileName);
     virtual bool vcsDelete(const QString &filename);
     virtual bool vcsCreateRepository(const QString &directory);
+    virtual QString vcsCreateSnapshot(const QString &topLevel);
+    virtual QStringList vcsSnapshots(const QString &topLevel);
+    virtual bool vcsRestoreSnapshot(const QString &topLevel, const QString &name);
+    virtual bool vcsRemoveSnapshot(const QString &topLevel, const QString &name);
 
     void emitRepositoryChanged(const QString &s);
     void emitFilesChanged(const QStringList &l);