New versions of the upstream code can't be imported. Real changes get hidden in the mass of reformatting. Format code consistently Use the same coding style as the code you are editing. This is a corollary to the previous subsection. It is easier for people reading the code if it uses consistent layout rules throughout, so when you are editing someone else's code the code you add should be in the same style.
Tabs are eight characters wide.
This is also a corollary to the previous subsections. Although indentation sizes vary greatly, tabs are almost universally eight characters, so using a different setting is liable to cause confusion or even reformatting. A four character tab might suit your indentation style, but the rest of the world will think your code is a mess. Comments Commit messages are not a substitute for comments, or vice versa. This makes it easier for people to know which version of a file they have and where it came from, so that they can usefully refer to the file's CVS history to find out about bugs and fixes, etc.