- *.stx are (mostly arbitrary) reference structured text files, and

- *.ref are previously processed output from the corresponding *.stx files.

Here's the in-depth explanation:

The directory has a bunch of .stx files (ones found on the zope.org
site, plus an 'examples.stx' file, for accumulating a body of
examples) plus corresponding .ref files, previously produced by a
prior, established StructuredText version.  The script 'regress'
applies the new ../StructuredText.py version to produce .new files,
and then compares the .ref files and the .new files, complaining if
any differences are found.

The intended procedure is to make your changes in ../StructuredText.py,
iron them out as best you can, and then try the regress script to
identify any unexpected functionality changes/backwards-compatability
losses.  (We also need to develop the body of reference text and examples.)

the update.

Added machinery for better permissions management.

quoting.

property sheets.

Also sort items in add list.

Added a new handy base class, SimpleItem, that has the
most popular standard ingredients pre-mixed.

property sheets managers.

property sheets.

Got rid of a number of obsolete and unused methods.

to support class instance method editing hijinks.

disabling index_html.

Changed the "add and edit" redirect to quote the id.  This is needed
to support class instance method editing hijinks.

  reorder(s, [with, without]]) --

     Reorder the items in s according to the order given in with
     and with items mentioned in without removed.  Items from s
     not mentioned in with are removed.

     s, with, and without are all either sequences if strings
     or sequences of key-value tuples, with ordering done on the
     keys.

This function is useful for constructing ordered select lists.

(By moving the indicator from OFS/main.dtml to here.

Added support for the optional variable 'manage_tabs_message',
which can be used to include status messages. This somewhat experimental
feature is provided in hopes of doing away with message dialogs.

Changed the way that highlighting is done in tabs to account
for the fact that view actions may now be paths, rather than just
method names.

Changed meta_types definition to use actual class meta-types.

meta-type.