logic: improved include detection

* also search for include paths of include directives extracted from header search paths
* extracted logic to gather unsolved includes
* extracted some code to filetree class

src/lib/utility/file/FileTree.h

@@ -0,0 +1,25 @@
+#ifndef FILE_TREE_H
+#define FILE_TREE_H
+
+#include <string>
+#include <set>
+#include <unordered_map>
+
+#include "utility/file/FilePath.h"
+
+class FileTree
+{
+public:
+	FileTree(const FilePath& rootPath);
+
+	FilePath getAbsoluteRootPathForRelativeFilePath(const FilePath& relativeFilePath);
+	std::vector<FilePath> getAbsoluteRootPathsForRelativeFilePath(const FilePath& relativeFilePath);
+
+private:
+	std::vector<FilePath> doGetAbsoluteRootPathsForRelativeFilePath(const FilePath& relativeFilePath, bool allowMultipleResults);
+
+	FilePath m_rootPath;
+	std::unordered_map<std::string, std::set<FilePath>> m_files;
+};
+
+#endif // FILE_TREE_H