message: Omit git version hash when git command fails
diff: @@ -28,6 +28,7 @@ fn commit_hash() -> Option<String> {
  .args(&["rev-parse", "--short", "HEAD"])
  .output()
  .ok()
  + .filter(|output| output.status.success())
  .and_then(|output| String::from_utf8(output.stdout).ok())
  .map(|hash| hash.trim().into())
  }
  