FolderNodes: Specify filter for Add Existing Directory

Allow foldernodes to specify which files they care for when doing
"Add Existing Directory". Before we used a fixed list with C++ header
and source files, which does make no sense for e.g. adding to resources.

Task-number: QTCREATORBUG-15278
Change-Id: I15dad133391485c2bcebd2d864623304b31b5f8f
Reviewed-by: Niels Weber <niels.weber@theqtcompany.com>

src/plugins/projectexplorer/projectnodes.cpp

@@ -309,6 +309,11 @@ void FolderNode::setIcon(const QIcon &icon)
     m_icon = icon;
 }
 
+QString FolderNode::addFileFilter() const
+{
+    return parentFolderNode()->addFileFilter();
+}
+
 bool FolderNode::addFiles(const QStringList &filePaths, QStringList *notAdded)
 {
     if (projectNode())
@@ -764,6 +769,11 @@ QList<ProjectNode*> SessionNode::projectNodes() const
     return m_projectNodes;
 }
 
+QString SessionNode::addFileFilter() const
+{
+    return QLatin1String("*.c; *.cc; *.cpp; *.cp; *.cxx; *.c++; *.h; *.hh; *.hpp; *.hxx;");
+}
+
 void SessionNode::addProjectNodes(const QList<ProjectNode*> &projectNodes)
 {
     if (!projectNodes.isEmpty()) {