git: init action, empty commit, jgit version up

[brig]

init repository with branch and empty commit:

    - task: git
      in:
        action: init
        url: https://github.com/brig/test.git
        initBranch: test
        workingDir: myRepo

    - task: git
      in:
        action: commit
        workingDir: myRepo
        auth: "..."
        baseBranch: "test"
        allowEmptyCommit: true
        commitMessage: "init message"
        commitUsername: "brig"
        commitEmail: "ybrigo@gmail.com"
        pushChanges: true