[Feature] Support branch checkout for Git remote hook

[leehuwuj]

Hi guys, Unlike the S3 or local file which we specify difference of Path corresponding to deployment environments, Git remote split them into difference branches, example, the main branch is stand for production, staging for non-production, etc,... I think it would be better if the GitRemoteHook support it. After checking the code, i think it can implement easily because the dulwich module has already support it. My idea is allow user specify the branch directly in the project_dir which is equal to the git project url and implement a additional function to extract the base url and the target branch on it. Example: https://github.com/tomasfarias/airflow-dbt-python/tree/staging -> project_url=https://github.com/tomasfarias/airflow-dbt-python.git branch=staging

Then specify the checkout=branch in dulwich's clone method: ex: client.clone(path, str(destination), mkdir=not destination.exists(), checkout=branch)

I feel free to make a PR for contribution.