"If you're not familiar with the kernel patch and
development process, here it is in a nutshell. People modify source
files to fix bugs, add or remove features, or adapt to changes in
the way the kernel handles certain tasks. They produce patch files
by using a utility called diff. diff compares the old source file
to the new one and produces a text file from the differences. You
can then distribute this text file to others, who can use it to
patch their source code with the utility called (what else?) patch.
Incidentally, the tradition for using patch to produce kernel
patch files is to add the command line switches -urN, which tells
diff to use the unified output format (which is what everyone on
the kernel development team uses), recurse through directories, and
keep track of new files that appear in one branch but not another.
The full command would be diff -Nru.
Until recently, kernel developers submitted their patch files by
including them within the body of an email message. Then they sent
the message to one or more kernel maintainers and/or the kernel
development mailing list. I'm not quite sure how the patch
submission process will change now that Linus Torvalds and others
are using the Bitkeeper Web-based source management system, but it
looks like they'll still rely largely on the diff"
