- `actions/checkout` runs `git checkout` on a specific commit SHA, meaning there is no "branch" by default, it's on a detached `HEAD`
  - so without a branch specified, it would error out
  - so specify a branch using [GH Actions env vars](https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables)
    - note that `$GITHUB_HEAD_REF` should exist for PRs, and dependabot makes PRs (vs. direct `push`es)
  - use `origin` as the remote name which is the default and also was mentioned in the error message

- also short-circuit the logic if there are no changes to `yarn.lock` (i.e. no deduplication neceessary)
  - this should also be less buggy as the later code will only execute when strictly necessary now (basically, when not needed, returns to the previous behavior before this step existed)

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

This reverts commit 7f5047d.

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: Anton Gilgur <agilgur5@gmail.com>

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>