Would you consider ref tag type without event?

Behaviour

Steps to reproduce this issue

Execute the action with only the ref tag type:
tags: | type=ref

Expected behaviour

Depending on the event, it should select the appropriate event type.
On a tag push, select the tag event type.
On a branch push, select the branch event type.

Actual behaviour

For now it fails with Missing event attribute for type=ref

Configuration

• Repository URL (if public):
• Build URL (if public):

on:
  push:
jobs:
  demo:
    steps:
      # Setup
      - uses: actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b  # v3.0.2
      - uses: docker/metadata-action@57396166ad8aefe6098280995947635806a0e6ea  # v4.1.1
        with:
          images: my_dummy_image
          tags: |
            type=ref

Logs

Download the log file of your build
and attach it to this issue.

No source file or test is named. Start by locating the tags input parsing and event-resolution entry points, then reproduce the configuration on push events for both a tag and a branch; done means type=ref works without an event attribute and selects the matching event type.