message: Allow `rev = "refs/..."` to use the GitHub fast path
diff: @@ -1029,10 +1029,14 @@ fn github_up_to_date(
  GitReference::Branch(branch) => branch,
  GitReference::Tag(tag) => tag,
  GitReference::DefaultBranch => "HEAD",
  - GitReference::Rev(_) => {
  - debug!("can't use github fast path with `rev`");
  + GitReference::Rev(rev) => {
  + if rev.starts_with("refs/") {
  + rev
  + } else {
  + debug!("can't use github fast path with `rev = \"{}\"`", rev);
  return Ok(false);
  }
  + }
  };
  // This expects GitHub urls in the form `github.com/user/repo` and nothing
  