index.js

import { getInput, setOutput, setFailed, warning } from "@actions/core";
import { Octokit } from "@octokit/rest";

try {
  const octokit = new Octokit({
    auth: getInput("github_token")
  });
  const [owner, repo] = process.env.GITHUB_REPOSITORY.split("/");
  octokit.rest.actions.listWorkflowRuns({
    owner,
    repo,
    workflow_id: getInput("workflow_id"),
    status: "completed",
    conclusion: "success",
    branch: getInput("branch"),
  }).then(({ data }) => {
    if (data.workflow_runs.length > 0) {
      setOutput("commit_sha", data.workflow_runs[0].head_sha);
    } else {
      warning("Unable to find last successful commit");
      setOutput("commit_sha", "");
    }
  }).catch((e) => {
    setFailed(e);
  });
} catch(e) {
  setFailed(e);
}