<!--- Verify first that your feature was not already discussed on GitHub -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### 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`


reference, refspec, git_version_used, verify_commit, separate_git_dir, result, gpg_whitelist, single_branch):
    ''' makes a new git repo if it does not already exist '''
    dest_dirname = os.path.dirname(dest)
    try:
        os.makedirs(dest_dirname)
    except Exception:
        pass