[O] Replace default category displayed in org-agenda with directory name

[Giacomo M]

Dear helpful list,

I'm experimenting with an org-agenda setup where I have a directory for 
each project, and a README.org with the project TODOs in each directory. 
I'm using the elisp below:

#+BEGIN_SRC: emacs-lisp

  (setq org-agenda-file-regexp "\\`README\\.org\\'")
  (setq org-agenda-files projectile-known-projects)

#+END_SRC

where I feed the list of directories of projects to org-agenda from 
projectile.

My question is: how can I rename the category of the TODOs listed in the 
agenda from "README.org" to the directory name containing the file of 
the TODOs (which in my setup would also identify the parent project)?

Thanks,

Giacomo