make taskdb.apply for create/delete not fail if already exists/doesn't exist

taskchampion/src/replica.rs

@@ -99,18 +99,25 @@ impl Replica {
             .map(move |tm| Task::new(uuid, tm)))
     }
 
-    /// Create a new task.  The task must not already exist.
+    /// Create a new task.
     pub fn new_task(&mut self, status: Status, description: String) -> anyhow::Result<Task> {
-        self.add_undo_point(false)?;
         let uuid = Uuid::new_v4();
-        let taskmap = self.taskdb.apply(SyncOp::Create { uuid })?;
-        trace!("task {} created", uuid);
-        let mut task = Task::new(uuid, taskmap).into_mut(self);
+        let mut task = self.create_task(uuid)?.into_mut(self);
         task.set_description(description)?;
         task.set_status(status)?;
+        trace!("task {} created", uuid);
         Ok(task.into_immut())
     }
 
+    /// Create a new, empty task with the given UUID.  This is useful for importing tasks, but
+    /// otherwise should be avoided in favor of `new_task`.  If the task already exists, this
+    /// does nothing and returns the existing task.
+    pub fn create_task(&mut self, uuid: Uuid) -> anyhow::Result<Task> {
+        self.add_undo_point(false)?;
+        let taskmap = self.taskdb.apply(SyncOp::Create { uuid })?;
+        Ok(Task::new(uuid, taskmap))
+    }
+
     /// Delete a task.  The task must exist.  Note that this is different from setting status to
     /// Deleted; this is the final purge of the task.  This is not a public method as deletion
     /// should only occur through expiration.