Locking non-existent paths. Time to discuss.

Even though it's very late in the game, there are some critical
decisions we need to make about locking features. They tend to
cascade out from each other.

* Fact: libsvn_fs allows already locks on non-existent paths. This
   feature exists to be interoperable with generic DAV clients. In DAV
   parlance, such things are called 'lock-null' resources. That is:
   they're 'null' resources (they don't exist), but are still locked.

* Fact: DAV clients expect to be able to PROPFIND on lock-null
   resources (to see the lock), and they also expect lock-null objects
   to be listed as children of directories. (Done by doing depth-1
   PROPFIND on a directory.) cmpilato and I are currently working on
   adding these behaviors to mod_dav_svn.

Question 1: Given that lock-null resources might exist, should svn
clients be able to see them? And to what extent?

     * 'svnadmin lslocks' already shows them.

     * 'svn status -u' shows remote locks on real files. Should it
       also show remote lock-null objects? This may prove very
       difficult to do; lundblad is working on it.

     * should 'svn info URL' show lock information if URL is a
       lock-null resource? It would be easy to do.

     * should 'svn ls' (i.e. svn_ra_get_dir()) show lock-null resources?

Question 2: Should the svn client (and API) be able to lock
nonexistent paths?

     * 'svn lock URL' is able to do this right now, though we could
       easily prevent it if we wanted to.

     * philip has argued that it would be useful to 'svn lock' a
       schedule-add file. While it may not prevent others from wasting
       time on conflicting schedule-adds, it *does* have the effect of
       reserving the whole path; that is, nobody can delete any parent
       directory of the schedule-add file.

cmpilato and I are running up against these questions on our quest to
make mod_dav_svn list lock-null children in directory listings.
Should mod_dav_svn only be showing these things to generic DAV
clients? Or should svn clients see them too? And if so, that would
mean making all three RA layers show lock-null children... and at that
point, perhaps svn_fs_dir_entries() should be returning them, right?

So we need to get these larger questions sorted out first.

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Received on Wed Mar 16 20:10:24 2005