Use case

You want to see all the changes which have been made to a single file in the project.

References

This was solved by a brighter mind than my own.
Daniel Hofstetter ‏@dhofstet on Twitter

Solution

git log -p <filename>

If you are using the most excellent SourceTree then you can select a file and go to Actions > Log selected to see a window of all the changes.

Success

Go make a brew!