Make checked out ref available to other steps

[jwgmeligmeyling]

Pull requests events by default check out the merge commit ref. Alternatively, the pull request head can be checkout using:

- uses: actions/checkout@v2
  with:
    ref: ${{ github.event.pull_request.head.sha }}

However, in successive actions it is not possible to detect whether the action uses another ref. github.context.sha still references the merge commit. See for example the discussion on: jwgmeligmeyling/pmd-github-action#2

It would be nice if actions/checkout@v2 somehow made the checkout ref available as output or exported variable.

Or am I overlooking an existing approach to obtain the checked out commit SHA?

[ericsciple]

git log -1 '--format=format:%H' works to get the current commit SHA

Although it assumes the sources were fetched using git (mainline). However when git 2.18 or higher isn't in the PATH, the tarball is downloaded instead.

[jwgmeligmeyling]

Exactly, so that's why that would only be a partial solution 😄 I think it also won't work in for example some Docker based tasks (unless the containers ship git). And obviously you need to execute the command in the work dir.

[Simran-B]

Looks like the short SHA is readily available:

checkout/src/github-api-helper.ts

Line 59 in 61b9e37

const archiveVersion = archiveFileNames[0] // The top-level folder name includes the short SHA

But getting the full one would require an API call I suppose?

[lucacome]

+1 for having the commit as an output of the action.

[lucacome]

I've opened #1180 to output ref and commit. Let me know what you think 🙏

[hvithval]

it would be nice to be able to access the actual commit-SHA/ SHORT_SHA and not the one that is created from the checkout source code step.

[jwgmeligmeyling]

it would be nice to be able to access the actual commit-SHA/ SHORT_SHA and not the one that is created from the checkout source code step.

That is already available as github.event.pull_request.head.sha.

[joshmgross]

This is now available in https://github.com/actions/checkout/releases/tag/v4.2.0