impl File.stage_persisted

pttodoest/src/main.rs

@@ -119,7 +119,11 @@ impl File {
     }
 
     fn stage_persisted(&self) -> Result<(), String> {
-        Err("not impl".to_string())
+        let stage = self.events()?.snapshot()?;
+        let plaintext = serde_yaml::to_string(&stage).unwrap();
+        let mut f = std::fs::File::create(&self.file).expect("failed to open file for writing");
+        writeln!(f, "{}", plaintext).expect("failed to write");
+        Ok(())
     }
 
     fn persist_stage(&self) -> Result<(), String> {