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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`


depth=dict(default=None, type='int'),
            clone=dict(default='yes', type='bool'),
            update=dict(default='yes', type='bool'),
            verify_commit=dict(default='no', type='bool'),
            gpg_whitelist=dict(default=[], type='list', elements='str'),
            accept_hostkey=dict(default='no', type='bool'),
            accept_newhostkey=dict(default='no', type='bool'),
            key_file=dict(default=None, type='path', required=False),
            ssh_opts=dict(default=None, required=False),
            executable=dict(default=None, type='path'),
            bare=dict(default='no', type='bool'),
            recursive=dict(default='yes', type='bool'),
            single_branch=dict(default=False, type='bool'),
            track_submodules=dict(default='no', type='bool'),
            umask=dict(default=None, type='raw'),
            archive=dict(type='path'),
            archive_prefix=dict(),
            separate_git_dir=dict(type='path'),
        ),
        mutually_exclusive=[('separate_git_dir', 'bare'), ('accept_hostkey', 'accept_newhostkey')],
        required_by={'archive_prefix': ['archive']},
        supports_check_mode=True
    )
    dest = module.params['dest']
    repo = module.params['repo']
    version = module.params['version']
    remote = module.params['remote']
    refspec = module.params['refspec']
    force = module.params['force']
    depth = module.params['depth']