When you have a newly introduced bug and you don’t know which git commit introduced it, what’s the best way to find that commit? Typically it’s easy enough to find an example of a commit for which the bug is not present (e.g. the last release) but finding the problematic commit between then and now is the hard part. If you have a set of 100 commits, and any commit could have introduced the bug, you could go through one by one, testing to see if the bug is present or not, but that’s inefficient! You’re better off picking the commit in the middle, seeing if it has the bug, and then narrowing down your search by a factor of two! So you’ll have 100 candidate commits, then 50, then 25, etc all the way down to one. Rather than checking 100 commits individually, you only need to check log₂(100) i.e. 7 commits.