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##### SUMMARY

The Git module encourages use of `StrictHostKeyChecking=no` with SSH, which makes the connection vulnerable to a MITM attack.

##### ISSUE TYPE

OpenSSH 7.5+ (2017-03-20) added a safer option which automatically accepts the key on first use but will not allow a MITM on subsequent connections: `StrictHostKeyChecking=accept-new` 

https://man.openbsd.org/ssh_config#StrictHostKeyChecking

It would be great if Ansible encouraged use of that mode by default in the documentation and to implement features such as the Git module's [`accept_hostkey`](https://github.com/ansible/ansible/blob/323d2adfcce9a53e906c2c4a40f6ac5fb32a0e68/lib/ansible/modules/git.py#L1103-L1108) feature.

##### ANSIBLE VERSION

```paste below
N/A
```

##### COMPONENT NAME
* `/modules/source_control/git.py`


""" Helper function for creating archive using git_archive """
    all_archive_fmt = {'.zip': 'zip', '.gz': 'tar.gz', '.tar': 'tar',
                       '.tgz': 'tgz'}
    _, archive_ext = os.path.splitext(archive)
    archive_fmt = all_archive_fmt.get(archive_ext, None)
    if archive_fmt is None:
        module.fail_json(msg="Unable to get file extension from "
                             "archive file name : %s" % archive,
                         details="Please specify archive as filename with "
                                 "extension. File extension can be one "
                                 "of ['tar', 'tar.gz', 'zip', 'tgz']")
    repo_name = repo.split("/")[-1].replace(".git", "")
    if os.path.exists(archive):
        
        
        
        tempdir = tempfile.mkdtemp()
        new_archive_dest = os.path.join(tempdir, repo_name)
        new_archive = new_archive_dest + '.' + archive_fmt
        git_archive(git_path, module, dest, new_archive, archive_fmt, archive_prefix, version)
        
        if filecmp.cmp(new_archive, archive):