16:9 is narrow enough why use more of it? Moves github header to the top right. Mouseover to see the search.

stylish.css

/**
Moves github header to the top right. mouseover to see the search.

1. Install the Stylish(https://chrome.google.com/webstore/detail/stylish/fjnbnpbmkenffdnngjfgmeleoegfcffe?hl=en) extension for Chrome.
2. Open up extension options and paste the whole CSS mentioned below.
3. Specify the domain name to be `github.com`.
4. Add a title and save.
*/

.header[role="banner"] {
  padding: 0;
}
.header>.container {
  width: 73px;
  margin-right: 15px;
  padding: 10px 15px;
  position: fixed;
    z-index: 50;
    right: 0;
}
.header>.container:hover .header-search {
  visibility: visible;
}
.header-search {
  visibility: hidden;
  height: 0;
  padding-bottom: 5px;
  position: relative;
    top: -28px;
    left: -370px;
}