cogito - how to drop a commit

I accidently commited too many files to my tree today, and now I want to
drop the commit so I have logically separate commits.

What is the right way to do this - in cogito hopefully.

I do not mind to execute a few git commands, but for my daily usage I
expect cogito to hanle everything and dropping a commit has proved
useful for me from time to time, so I expect it be be implemented in the
porcelain somehow.

I have read the help for cg-seek - but it di not convince me to be what
I seeked.

	Sam