Ediff is a great tool for diffing to files/buffers and merging changes. One thing I liked is that you can make it ignore white-space only differences. I used to do activate it every time. Finally I got to the point that I wanted to make the change permanent, so I followed EmacsWiki advice:
Whitespace sensitivity – Include ‘-w’ in ‘ediff-diff-options’.
So, I did a quick
(setq...) but it didn’t work. After some googling, I came across this message. Seems like you have to make the changes using customize, otherwise it won’t work. So, if somebody else is having this problem, making the changes using customize (
M-x customize-group RET ediff-diff) is the way to go.