Search for changes in a file

The pickaxe command -S searches for files.
Pickaxe also handles regex. NOTE: I need to understand regex for good after so many years.

But any of these changes can be made more specific with a file reference.
git log -- <reference to the file>
git show <commit hash> -- <reference to the file>

in both these cases, we are filtering the results by the file name, which is cool.