Revision 1663738

Don't expose internal transaction properties like 'svn:check-locks' through
the public FS API and error out on attempts to change them.

When creating a transaction, a caller can specify one or multiple flags like
SVN_FS_TXN_CHECK_LOCKS.  These flags affect how the transaction behaves
when being prepared or committed.  For example, a caller can tell us that
she/he doesn't want the back end to perform on-the-fly lock checking or might
want to specify the final 'svn:date' value for the transaction.  We want to
persist these flags even if a transaction is reopened — that's why we map
them into a set of internal transaction properties, set these properties when
a transaction is created, and drop them just before the commit.

Prior to this changeset these internal properties were a part of what our
FS API returns, and we also allowed changing them (while being particularly
picky about 'svn:client-date', as any attempts to change it were silently
discarded).  Instead of that, now we filter out *all* internal transaction
properties in functions like svn_fs_txn_prop() or svn_fs_txn_proplist(), and
we also forbid changing them with svn_fs_change_txn_prop() / _txn_props().

We don't need this ourselves, and we no longer allow arbitrary FS API
callers to mess with our private implementation details.  Furthermore, this
makes the property setters do what they were told to do or fail.  This is a
better choice compared to silently stripping out 'svn:client-date' changes
and saying that everything went fine.  As a caller, I'd expect a successful
call to mean that the requested changes were applied without any problems,
and that's the behavior we get with this patch.

See related discussion in http://svn.haxx.se/dev/archive-2015-03/0003.shtml
Subject: [RFC/PATCH] Modifying internal FS transaction properties

* subversion/libsvn_fs/fs-loader.c
  (is_internal_txn_prop): New helper function.
  (svn_fs_txn_prop, svn_fs_txn_proplist): Do not return internal txn
   properties to the caller.
  (svn_fs_change_txn_prop): Error out on attempts to change internal txn
   properties.
  (svn_fs_change_txn_props): Error out on attempts to change internal
   txn properties.  Instead of silently skipping 'svn:client-date' changes,
   we now use "all-or-nothing" approach and can drop the property filtering
   code.

* subversion/tests/libsvn_fs/fs-test.c
  (commit_timestamp): Don't test what happens if we try to alter the
   'svn:client-date' property here.  This (and other possible scenarios)
   should now be covered by ...
  (test_internal_txn_props): ...this new test.
  (test_funcs): Reference new test.

* subversion/tests/cmdline/svnlook_tests.py
  (test_txn_flag): Adjust the test expectation, as we no longer leak
   internal svn:check-locks values for the transactions.