<!--- 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 -->

'''
    Determine what branch HEAD is associated with.  This is partly
    taken from lib/ansible/utils/__init__.py.  It finds the correct
    path to .git/HEAD and reads from that file the branch that HEAD is
    associated with.  In the case of a detached HEAD, this will look
    up the branch in .git/refs/remotes/<remote>/HEAD.
    '''
    try:
        repo_path = get_repo_path(dest, bare)
    except (IOError, ValueError) as err:
        
        """``.git`` file does not have a valid format for detached Git dir."""
        module.fail_json(
            msg='Current repo does not have a valid reference to a '
            'separate Git dir or it refers to the invalid path',
            details=to_text(err),
        )
    
    
    
    headfile = os.path.join(repo_path, "HEAD")
    if is_not_a_branch(git_path, module, dest):
        headfile = os.path.join(repo_path, 'refs', 'remotes', remote, 'HEAD')
    branch = head_splitter(headfile, remote, module=module, fail_on_error=True)
    return branch
def get_remote_url(git_path, module, dest, remote):