>> +- a cons-cell, where the car describes how to interpret the cdr.
>> +  The car can be one of the following:
>> +  * `major-mode': the buffer matches if the buffer's major
>> +    mode is eq to the cons-cell's cdr
>> +  * `derived-mode': the buffer matches if the buffer's major
>> +    mode is derived from the major mode denoted by the cons-cell's
>> +    cdr
>
> Do we really need both major-mode and derived-mode?

It seems to have been useful in project.el, see
`project-kill-buffer-conditions'.  In that case you want to both be able
to say something like "kill buffers only if they are in
fundamental-mode", but also something like "kill all buffers that are
based on comint-mode".

-- 
	Philip Kaludercic