Where to start with recursive file operations

[Andrei Stebkov]

Hi!

I would like to write a function that finds files recursively starting from
the current directory, opens files based on given extension and does some
operations on them. For instance, checks out the file (from CVS or
Perforce), selects the whole buffer, indents the contents and save it.
Also I'd like to have same kind of function that would search and replace in
multiple files. 
As all the problems that I listed here stem from the same root (recursive
search) I need a few pointers about the basic built-in emacs functions of
this domain. The function of this nature must be already written, I just
couldn't find them.

Thanks in advance,
Andrei