message: Rename variables and remove std::mem
diff: -use std::mem;
  use std::sync::{mpsc, Arc, Mutex};
  use crate::commands;
  @@ -16,17 +15,16 @@ pub fn watch_for_changes(
  session_id: &str,
  verbose: bool,
  ) -> Result<(), failure::Error> {
  - let (tx, rx) = mpsc::channel();
  - commands::watch_and_build(&target, Some(tx))?;
  + let (sender, receiver) = mpsc::channel();
  + commands::watch_and_build(&target, Some(sender))?;
  - while let Ok(_) = rx.recv() {
  + while let Ok(_) = receiver.recv() {
  let user = user.clone();
  let target = target.clone();
  commands::build(&target)?;
  - let mut p = preview_id.lock().unwrap();
  - *p = get_preview_id(target, user, server_config, session_id, verbose)?;
  - mem::drop(p);
  + let mut preview_id = preview_id.lock().unwrap();
  + *preview_id = get_preview_id(target, user, server_config, session_id, verbose)?;
  }
  Ok(())
  