message: feat: simplify git describe info in version
  The full `git describe` output easily cause confusing, this change will only
  show the 7 hex digests commit sha and the dirty flag, such as
  ckb 0.15.0-pre (rylai-v4 d7d3baca-dirty 2019-06-06)
diff: @@ -60,7 +60,7 @@ impl std::fmt::Display for Version {
  pub fn get_commit_describe() -> Option<String> {
  std::process::Command::new("git")
  - .args(&["describe", "--dirty"])
  + .args(&["describe", "--dirty", "--always", "--exclude", "*"])
  .output()
  .ok()
  .and_then(|r| {
  