I've several directories (say, a,b,c,d and e on the top level. They're quite capacious inside with many nested levels. I need to delete all but two.
I set exclude to "a" and "c" and the cleaning process takes very much time, rm -rf works much faster, so i assume it's not a general performance issue.

I don't want to look what the algorithm is, but maybe it's not optimal if it tries to check any pathname. On the other hand maybe i should write something like a/** and c/**?