Add source code.

include/Config.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <string>
+
+// User preferences stored outside the database, in
+// $XDG_CONFIG_HOME/task_tracker (or ~/.config/task_tracker, or %APPDATA%).
+class Config {
+public:
+    Config();
+
+    void load();
+    void save() const;
+
+    const std::string& editor() const;  // empty = use the default
+    void setEditor(const std::string& command);
+
+    std::string historyPath() const;
+
+    static std::string directory();
+
+private:
+    std::string directory_;
+    std::string editor_;
+};