This is a tree of files and directories which is used in Subversion python tests. It is called so because of files of this tree which are called after names of different letters of the Greek alphabet. This tree can be represented as follows:

                                         Repository Root
                                            ____|____
                                           /         \
                                          /           \
                                         /             \
                                        A             iota
               _______________________//|\
              /         ______________/ | \_____________
             mu        /                |               \
                      /                 |                \
                     B                  C                 D
               _____/|\_____                _____________/|\
              /      |      \              /              | \
             /       |       \            /              /   \
          lambda     |        F          /              /     \
                     E                gamma            /       \
                    / \                               /         \ 
                   /   \                     ________/           \________
               alpha   beta                 /                             \           
                                           /                               \
                                          /                                 \
                                         G                                   H
                                ________/|\_______                   _______/|\______
                               /         |        \                 /        |       \                       
                              /          |         \               /         |        \
                             /           |          \             /          |         \
                            pi          rho         tau          chi        psi       omega