Using Git bisect to figure out when brokenness was introduced

I did a fresh installation of Drupal 8 this morning and came across a bit of ugliness: an ugly grey border on the home page, caused by an empty div being inserted into the page:

My last fresh install of Drupal 8 was about a week ago and didn't have this problem. I didn't relish the idea of going through all of the commits since then one-by-one to figure out where this bug was introduced.

Enter the git bisect command! The bisect command works by performing a "binary" search between one state of the code and the other in order to find, by process of elimination, where a given problem was introduced. It's quick, it's easy, and by golly it just works!

Here's how to use git bisect, step-by-step!

read more