Github API: Create a branch from another branch

[hemanLMG]

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Hi, I'm attempting to use the GitHub Octokit REST library to create a branch from another branch. Essentially, I'm trying to cut a release branch from my base branch. I attempted to use the createRef endpoint with the following options:

    const branch = await octokitApi.rest.repos.getBranch({
      owner,
      repo,
      branch: baseBranch
    });

    const releaseBranch = await octokitApi.git.createRef({
      owner,
      repo,
      ref: `refs/heads/${releaseBranchName}`,
      sha: branch.data.commit.sha
    });

The issue is that the base branch head commit SHA only includes the latest commit of the base branch. How can I retrieve all changes from the base branch to the new release branch? Essentially, I'm seeking the same functionality as when creating a branch from the GitHub UI