Enable cloning a repo from a specific commit SHA

[TamimiGitHub]

I would like to have the ability to clone a repo from a predefined commit

    {
      resolve: `gatsby-source-git`,
      options: {
        name: `repo-one`,
        remote: `https://bitbucket.org/stevetweeddale/markdown-test.git`,
        commit: `e05270aa0927691d797edcebbf1d7fa33fc91516`,
      }
    }