Weird commit checked out during pull request trigger

[pantelis-karamolegkos]

This is my trigger

on:
  pull_request:
    branches:
      - master

So I have an open PR targeting master from the branch my-feature

The tip of my branch is:

835e4b8 (HEAD ->my-feature origin/my-feature) Reset

I also noticed the following in the logs

 HEAD is now at c1d3b56 Merge 835e4b8 into a2f6789

where a2f6789 is the tip of the master.

Why is it using a distinct commit for the PR?

All the actions from that point on operate on this commit c1d3b56

[adamk9k]

I'm seeing the same thing, it's essentially a merge commit from the parent branch.

I'm using

- uses: 'actions/checkout@v3'
   with:
     ref: ${{ github.event.pull_request.head.sha }}

for the time being to get around this bug.

Other parameters:

• the action I saw this happen is using a self-hosted runner
• potentially related to 47fbe2d

[pantelis-karamolegkos]

Could it be that this has to do with the action operating on a (merge) commit that is being created (when the head branch is merged into the base branch)?

[adamk9k]

In my case at least, we don't have merge commits on the repo, we rebase and the checkout itself seems to create a merge commit

[ramnes]

Seen this as well, and that's super confusing indeed. Looks like the action tries to merge with the target branch before continuing.

Seems related (or identical) to #237, #299, #626, #504, #881, #1325, and probably others.