Revive TDB2::has and TF2::has methods

This reverts commit fa920f02aa. Methods
found their usage after all.

src/TDB2.cpp

@@ -149,6 +149,19 @@ bool TF2::get (const std::string& uuid, Task& task)
   return false;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+bool TF2::has (const std::string& uuid)
+{
+  if (! _loaded_tasks)
+    load_tasks ();
+
+  for (auto& i : _tasks)
+    if (i.get ("uuid") == uuid)
+      return true;
+
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 void TF2::add_task (Task& task)
 {
@@ -1350,6 +1363,14 @@ bool TDB2::get (const std::string& uuid, Task& task)
          completed.get (uuid, task);
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// Locate task by UUID, wherever it is.
+bool TDB2::has (const std::string& uuid)
+{
+  return pending.has (uuid) ||
+         completed.has (uuid);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 const std::vector <Task> TDB2::siblings (Task& task)
 {

src/TDB2.h

@@ -50,6 +50,7 @@ public:
 
   bool get (int, Task&);
   bool get (const std::string&, Task&);
+  bool has (const std::string&);
 
   void add_task (Task&);
   bool modify_task (const Task&);
@@ -121,6 +122,7 @@ public:
   const std::vector <Task> all_tasks ();
   bool get (int, Task&);
   bool get (const std::string&, Task&);
+  bool has (const std::string&);
   const std::vector <Task> siblings (Task&);
   const std::vector <Task> children (Task&);