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

##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
The `ssh_opts` parameter relies on setting environment variables for git, such as GIT_SSH. Git did not recognize this environment variable until version 2.3.0 (see https://git-scm.com/docs/git/2.3.0), and many contemporary OSes (RHEL 7, CentOS7) include older versions of Git (1.8.3.1).

It would be useful to provide a warning in this case, similar to the warning for the `depth` parameter. E.g. "Your git version is too old to support the ssh_opts argument."

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
git.py
source control, git module

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
It would save users time when trying to troubleshoot failed git connections via SSH.

<!--- Paste example playbooks or commands between quotes below -->
```yaml
- name: clone a git repo
  git:
    repo: git@github.com:cherdt/hello_ansible.git
    dest: /opt/hello_ansible
    version: master
    ssh_opts: "{{-o IdentityFile=github_id_rsa}}"
```

<!--- HINT: You can also paste gist.github.com links for larger files -->

if path is None:
        return None
    
    return os.path.normpath(os.path.realpath(os.path.expanduser(os.path.expandvars(path))))
def get_submodule_update_params(module, git_path, cwd):
    
    
    
    params = []
    
    cmd = "%s submodule update --help" % (git_path)
    rc, stdout, stderr = module.run_command(cmd, cwd=cwd)
    lines = stderr.split('\n')
    update_line = None
    for line in lines:
        if 'git submodule [--quiet] update ' in line:
            update_line = line
    if update_line:
        update_line = update_line.replace('[', '')
        update_line = update_line.replace(']', '')
        update_line = update_line.replace('|', ' ')
        parts = shlex.split(update_line)
        for part in parts:
            if part.startswith('--'):
                part = part.replace('--', '')
                params.append(part)
    return params
def write_ssh_wrapper(module_tmpdir):