struct root_vtable_t documentation

Hi all,

I just came across

struct root_vtable_t
in
subversion/libsvn_fs/fs-loader.h

and found it totally underdocumented. AFAICT, that's a pretty central
internal API, but reading it leaves many questions. An extract:

libsvn_fs/fs-loader.h
[[[
/* Some of these operations accept multiple root arguments. Since the
   roots may not all have the same vtable, we need a rule to determine
   which root's vtable is used. The rule is: if one of the roots is
   named "target", we use that root's vtable; otherwise, we use the
   first root argument's vtable. */
typedef struct root_vtable_t
{
  [...]
  /* Files */
  svn_error_t *(*file_length)(svn_filesize_t *length_p, svn_fs_root_t *root,
                              const char *path, apr_pool_t *pool);
  svn_error_t *(*file_checksum)(svn_checksum_t **checksum,
                                svn_checksum_kind_t kind, svn_fs_root_t *root,
                                const char *path, apr_pool_t *pool);
  svn_error_t *(*file_contents)(svn_stream_t **contents,
                                svn_fs_root_t *root, const char *path,
                                apr_pool_t *pool);
  svn_error_t *(*make_file)(svn_fs_root_t *root, const char *path,
                            apr_pool_t *pool);
  svn_error_t *(*apply_textdelta)(svn_txdelta_window_handler_t *contents_p,
                                  void **contents_baton_p,
                                  svn_fs_root_t *root, const char *path,
                                  svn_checksum_t *base_checksum,
                                  svn_checksum_t *result_checksum,
                                  apr_pool_t *pool);
  [...]
]]]

It just says "Files", but I want to know what happens when I call, say,
apply_textdelta(), in detail. Where does the new data go? Is a new revision
tree node created? What Where How?

I need to start looking up implementations (pretty cumbersome for a vtable)
to find out what is going on.

Would someone in the know like to document these callbacks, or am I looking
in the wrong place or something?

Thanks
~Neels

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