<!--- 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 -->

''' updates repo from remote sources '''
    set_remote_url(git_path, module, repo, dest, remote)
    commands = []
    fetch_str = 'download remote objects and refs'
    fetch_cmd = [git_path, 'fetch']
    refspecs = []
    if depth:
        
        
        currenthead = get_head_branch(git_path, module, dest, remote)
        if refspec:
            refspecs.append(refspec)
        elif version == 'HEAD':
            refspecs.append(currenthead)
        elif is_remote_branch(git_path, module, dest, repo, version):
            if currenthead != version:
                
                
                
                refspecs.append('+refs/heads/%s:refs/heads/%s' % (version, version))
            refspecs.append('+refs/heads/%s:refs/remotes/%s/%s' % (version, remote, version))
        elif is_remote_tag(git_path, module, dest, repo, version):
            refspecs.append('+refs/tags/' + version + ':refs/tags/' + version)