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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`


'''
    Determine what branch HEAD is associated with.  This is partly
    taken from lib/ansible/utils/__init__.py.  It finds the correct
    path to .git/HEAD and reads from that file the branch that HEAD is
    associated with.  In the case of a detached HEAD, this will look
    up the branch in .git/refs/remotes/<remote>/HEAD.
    '''
    try:
        repo_path = get_repo_path(dest, bare)
    except (IOError, ValueError) as err:
        
        """``.git`` file does not have a valid format for detached Git dir."""
        module.fail_json(
            msg='Current repo does not have a valid reference to a '
            'separate Git dir or it refers to the invalid path',
            details=to_text(err),
        )
    
    
    
    headfile = os.path.join(repo_path, "HEAD")
    if is_not_a_branch(git_path, module, dest):
        headfile = os.path.join(repo_path, 'refs', 'remotes', remote, 'HEAD')
    branch = head_splitter(headfile, remote, module=module, fail_on_error=True)
    return branch
def get_remote_url(git_path, module, dest, remote):