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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`


if module.check_mode or not allow_clone:
            remote_head = get_remote_head(git_path, module, dest, version, repo, bare)
            result.update(changed=True, after=remote_head)
            if module._diff:
                diff = get_diff(module, git_path, dest, repo, remote, depth, bare, result['before'], result['after'])
                if diff:
                    result['diff'] = diff
            module.exit_json(**result)
        
        clone(git_path, module, repo, dest, remote, depth, version, bare, reference,
              refspec, git_version_used, verify_commit, separate_git_dir, result, gpg_whitelist, single_branch)
    elif not update:
        
        
        
        result['before'] = get_version(module, git_path, dest)
        result.update(after=result['before'])
        if archive:
            
            
            if module.check_mode:
                result.update(changed=True)
                module.exit_json(**result)
            create_archive(git_path, module, dest, archive, archive_prefix, version, repo, result)
        module.exit_json(**result)
    else:
        
        local_mods = has_local_mods(module, git_path, dest, bare)
        result['before'] = get_version(module, git_path, dest)
        if local_mods: