Undoing merges

Hi git list,

I hope this isn't a double post. I couldn't get a response from this mailing list with Outlook.

I'm trying to find out how to undo a merge. I know that my branches are independent and that I can just carry on working on them and merge again later, but I'm just trying to keep my revision graph tidier. Should I even be undoing merges?

I've searched around, but I can seem to find an answer I can follow.

Regards,

Richard