How to get the zipballUrl of a branch using github graphQL API?

I am trying to programmatically download a zip file of a repository which is already checked out to a specific branch. For that I need to obtain the zipballUrl of the head of the branch I specify through github graphQL API.

This answer specifies how to get the zipballUrl of the default branch but I could not alter it to my requirement. Appreciate if someone can help out.

PS: Running a git clone command and checking out to branch is not an option because the programming language I use (ballerina) does not support shell commands yet.

You can use the reference field of the repository object.

For example, considering the same google gson project

{
  repository(owner: "google", name: "gson") {

    ref(qualifiedName: "722"){
      target {
        ... on Commit {
          tarballUrl
          zipballUrl
        }
      }
    }
  }
}

In this query ref(qualifiedName) will basically look for the reference or branch name with the specified value and return the tar content of the branch.

Response

{
  "data": {
    "repository": {
      "ref": {
        "target": {
          "tarballUrl": "https://codeload.github.com/google/gson/legacy.tar.gz/2725be440147a71030ece93683b4424e849c59ed",
          "zipballUrl": "https://codeload.github.com/google/gson/legacy.zip/2725be440147a71030ece93683b4424e849c59ed"
        }
      }
    }
  }
}

you can verify the sha of the branch reference "722" https://github.com/google/gson/commit/2725be440147a71030ece93683b4424e849c59ed