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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`


try:
        
        
        if os.access(module_tmpdir, os.W_OK | os.R_OK | os.X_OK):
            fd, wrapper_path = tempfile.mkstemp(prefix=module_tmpdir + '/')
        else:
            raise OSError
    except (IOError, OSError):
        fd, wrapper_path = tempfile.mkstemp()
    fh = os.fdopen(fd, 'w+b')
    template = b("""#!/bin/sh
if [ -z "$GIT_SSH_OPTS" ]; then
    BASEOPTS=""
else
    BASEOPTS=$GIT_SSH_OPTS
fi
# Let ssh fail rather than prompt
BASEOPTS="$BASEOPTS -o BatchMode=yes"
if [ -z "$GIT_KEY" ]; then
    ssh $BASEOPTS "$@"
else
    ssh -i "$GIT_KEY" -o IdentitiesOnly=yes $BASEOPTS "$@"
fi
""")
    fh.write(template)
    fh.close()
    st = os.stat(wrapper_path)
    os.chmod(wrapper_path, st.st_mode | stat.S_IEXEC)
    return wrapper_path
def set_git_ssh(ssh_wrapper, key_file, ssh_opts):