Git commit partitioning

Problem statement

You need to add functionality to an existing code base or fix a defect. How do you decide which changes go into which git commit?

Guidelines

Guildeline	Reason
The code should build and run after each commit.	This allows the git bisect command to work as expected.
There should only be one functional change per commit.	This makes the code easier to review. If the commit introduces an error, it is much more obvious what is the source of the error and how to fix it.
The first commit often cleans up the code match the coding standard.	If you touching the code, make it better. There should be no functional change.
The second commit often refactors the code without changing the functionality.	This makes it more straight forward to understand the commits that fix the defect or adds new functionality.