message: Add rustup pull command
diff: @@ -29,11 +29,27 @@ case $1 in
  "push")
  cg_clif=$(pwd)
  pushd ../rust
  - branch=update_cg_clif-$(date +%Y-%m-%d)
  + git pull origin master
  + branch=sync_cg_clif-$(date +%Y-%m-%d)
  git checkout -b "$branch"
  git subtree pull --prefix=compiler/rustc_codegen_cranelift/ https://github.com/bjorn3/rustc_codegen_cranelift.git master
  git push -u my "$branch"
  +
  + # immediately merge the merge commit into cg_clif to prevent merge conflicts when syncing
  + # from rust-lang/rust later
  + git subtree push --prefix=compiler/rustc_codegen_cranelift/ "$cg_clif" sync_from_rust
  + popd
  + git merge sync_from_rust
  + ;;
  + "pull")
  + cg_clif=$(pwd)
  + pushd ../rust
  + git pull origin master
  + rust_vers="$(git rev-parse HEAD)"
  + git subtree push --prefix=compiler/rustc_codegen_cranelift/ "$cg_clif" sync_from_rust
  popd
  + git merge sync_from_rust -m "Sync from rust $rust_vers"
  + git branch -d sync_from_rust
  ;;
  *)
  echo "Unknown command '$1'"
  