message: Add seconds() method to Timestamp
diff: @@ -42,14 +42,21 @@ impl Timestamp {
  }
  /// Returns nanoseconds since epoch
  + #[inline]
  pub fn nanos(&self) -> u64 {
  self.0.u64()
  }
  +
  + /// Returns seconds since epoch (truncate nanoseconds)
  + #[inline]
  + pub fn seconds(&self) -> u64 {
  + self.0.u64() / 1_000_000_000
  + }
  }
  impl fmt::Display for Timestamp {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  - let whole = self.nanos() / 1_000_000_000;
  + let whole = self.seconds();
  let fractional = self.nanos() % 1_000_000_000;
  write!(f, "{}.{:09}", whole, fractional)
  }
  @@ -131,6 +138,14 @@ mod tests {
  assert_eq!(sum.nanos(), 0);
  }
  + #[test]
  + fn timestamp_seconds() {
  + let sum = Timestamp::from_nanos(987654321000);
  + assert_eq!(sum.seconds(), 987);
  + let sum = Timestamp::from_seconds(1234567).plus_nanos(8765436);
  + assert_eq!(sum.seconds(), 1234567);
  + }
  +
  #[test]
  fn timestamp_implements_display() {
  let embedded = format!("Time: {}", Timestamp::from_nanos(0));
  