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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`


cmd = [git_path, 'clone']
    if bare:
        cmd.append('--bare')
    else:
        cmd.extend(['--origin', remote])
    is_branch_or_tag = is_remote_branch(git_path, module, dest, repo, version) or is_remote_tag(git_path, module, dest, repo, version)
    if depth:
        if version == 'HEAD' or refspec:
            cmd.extend(['--depth', str(depth)])
        elif is_branch_or_tag:
            cmd.extend(['--depth', str(depth)])
            cmd.extend(['--branch', version])
        else:
            
            module.warn("Ignoring depth argument. "
                        "Shallow clones are only available for "
                        "HEAD, branches, tags or in combination with refspec.")
    if reference:
        cmd.extend(['--reference', str(reference)])
    if single_branch:
        if git_version_used is None:
            module.fail_json(msg='Cannot find git executable at %s' % git_path)
        if git_version_used < LooseVersion('1.7.10'):
            module.warn("git version '%s' is too old to use 'single-branch'. Ignoring." % git_version_used)
        else:
            cmd.append("--single-branch")
            if is_branch_or_tag:
                cmd.extend(['--branch', version])
    needs_separate_git_dir_fallback = False
    if separate_git_dir: