Code blocks not rendered properly in smaller screens

I noticed an issue in which the code block in the "git log --oneline improvements" section renders badly in smaller screen. Further it also breaks the single-pagedness of the website. As a consequence, one might have to zoom in to read the post and scrolling might take you to empty space in the right. Screen shots:

• Desktop view:
  

• Mobile view (iPhone SE resolution)
  

  

  Note the scroll bar in the bottom of the page.

It would be nice to fix this by making the code blocks render in such a way that the code within the block is scrollable rather than the whole page being scrollable.

Note: Initially mentioned in https://github.com/git/git.github.io/pull/366#issuecomment-471316738

从链接的 Git Developer Pages 网站上的“git log --oneline improvements”部分开始，按照截图中显示的 iPhone SE 分辨率复现布局。检查影响代码块的响应式样式；完成标准是代码本身可以水平滚动，而不会造成整个页面溢出或产生空白区域。