Preventing “double” borders in CSS

Question

Say I have two divs next to each other (take https://chrome.google.com/webstore/category/home as reference) with a border.

Is there a way (preferably a CSS trick) to

Answer 1

If the divs all have the same class name:

div.things {
    border: 1px solid black;
    border-left: none;
}

div.things:first-child {
    border-right: 1px solid black;
}

There's a JSFiddle demo here.