picocli/docs/quick-guide-docinfo.html

<style>
 .listingblock:hover .clipboard {
     display: block;
 }

 .clipboard {
     display: none;
     border: 0;
     font-size: .75em;
     text-transform: uppercase;
     font-weight: 500;
     padding: 6px;
     color: #999;
     position: absolute;
     top: .425rem;
     right: .5rem;
     background: transparent;
 }

 code + .clipboard {
    top: -0.05rem !important;
     right: 3rem !important;
 }

 .clipboard:hover, .clipboard:focus, .clipboard:active {
     outline: 0;
     background-color: #eee9e6;
 }
</style>
<script>
$(function() {

var pre = document.getElementsByTagName('pre');
for (var i = 0; i < pre.length; i++) {
    var b = document.createElement('input');
    b.setAttribute('role', 'button');
    b.setAttribute('type', 'button');
    b.value = 'Copy';
    b.className = 'clipboard';

    if (pre[i].childNodes.length === 1 && pre[i].childNodes[0].nodeType === 3) {
        var div = document.createElement('div');
        div.textContent = pre[i].textContent;
        pre[i].textContent = '';
        pre[i].appendChild(div);
    }
    pre[i].appendChild(b);
 }

new ClipboardJS('.clipboard', {
    text: function(b) {
        return b.parentNode.innerText;
    }
}).on('success', function(e) {
        e.clearSelection();
        e.trigger.value = 'Copied';
        setTimeout(function() {
            e.trigger.value = 'Copy';
        }, 2000);
    });
});
</script>