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Re: Subversion support

From: Greg Stein <gstein@lyra.org>
Date: Fri, 22 Dec 2000 01:12:54 -0800
To: "Geoffrey M. Clemm" <geoffrey.clemm@rational.com>
Cc: ietf-dav-versioning@w3.org
Message-ID: <20001222011254.Y22947@lyra.org>
On Thu, Dec 21, 2000 at 11:32:32AM -0500, Geoffrey M. Clemm wrote:
>    From: Greg Stein <gstein@lyra.org>
>...
>    24.xxx  Subversion 1.0 (http://subversion.tigris.org/)
> 
>       A. Subversion client
> 	 i. Required options:
> 	    a. RFC 2518, Class 1  (but not Class 2)
> 	    b. Core versioning (but not: VERSION-CONTROL, UNCHECKOUT, or
> 	       SET-TARGET)
> 	    c. Client-Workspace option
> 	    d. Label option  (probably; not entirely sure because our "label"
> 	       may simply be a COPY)
> 	       [ this also presumes Label will be split from Client-WS ]
> 
> Yes, the label option is split from client-ws option.  I think you'll
> end up wanting to support the baseline option instead of the label option,
> but that is of course up to you.

Yup. Not sure on Labels, and baselines will probably be post-1.0. I'll take
a look at them (with your feedback to the SVN list) and see if/how they
apply and whether there is any "impedance" with introducing baselines.

> 	    e. Activity option
> 	    f. Version-History-Resource option
> 	    g. Version-Controlled-Collection option
> 	    h. Fork-Control option
> 	    i. Subversion-specific items: a custom report,
> 
> I'd be interested in hearing about the custom report.

I'm reporting the status of the client files to the server as the *input*,
and it returns information about what is out of date.

The status report is somewhat compressed. For example, "this dir (and
everything in it) is v7, except <this> file is v8 and <that> is v6." The
server then returns info for each item that needs to be updated. These
updates are in one of two forms:

1) the client side resource is up to date, except its version has changed.
   <here> is the new version URL and version-name (where the version-name is
   actually the repository-global version number)

or

2) the resource is out of date. here is the version URL and version-name.
   [ the client then fetches a diff to patch from the old version up to the
     new version ]

Case (1) happens a lot when you have global version numbers (foo.c gets
updated, which causes a global version bump, which means every version URL
must be updated to the new version number). I might have to figure out a way
to compress the response. Either let the version URL stagnate, or tell the
client how to reconstruct version URLs for <all files in this subtree>.

In any case... the basic scenario is to report the client state to the
server, and have the server tell the client what is needed to update itself.

[ yes, this can be made interoperable through the use of PROPFIND, but you
  would need to PROPFIND across the whole repository to look for updates. we
  send a compressed state and the server tells what bits will need to be
  updated ]

> 	       DAV:version-name must be an integer representing
> 	       repository-global-change,
> 
> DAV:version-name is server defined, so that can be whatever you want
> it to be.

On the server, yes. I put this under "required client options." The client
*expects* this to be an integer.

> 	       atomic CHECKIN of activities,
> 
> I added atomic checkin of activities in the MERGE
> request, so that's now part of the activity option.

Hmm. I read the new draft. I'm unsure if the "MERGE <activity>" does the
checkin now. It seems to imply that a merge of an activity will cause all
checked-out resources to be checked in first, then the merge to the VCR is
performed.

Is that the general sense?

(presuming so, then I can review it to assist with clarifying it)

> 	       DAV:prop supported within the DAV:checkin
> 	       element (to enable returning post-checkin information, such as
> 	       new version resource URLs),
> 
> I believe you can get this information by using a property REPORT
> on the DAV:version-set of the activity.  We should verify this.

If the activity sticks around after a CHECKIN or MERGE, then yah... I'd have
the version-set. Sounds about right.

>...
> UNCHECKOUT and SET-TARGET are no longer in core,

Cool. No need to worry about them, then :-)

Hmm. I see CHECKOUT isn't there either... off in the client/server workspace
options. Quick question/point: what should a server return for a CHECKOUT
against the wrong type of resource? e.g. should I return 409 (Conflict) if
somebody does a CHECKOUT on a VCR? Is there a specific <DAV:error code> to
return for this situation?

> and since Subversion
> auto-version-controls, you actually *do* support VERSION-CONTROL (i.e.
> applying VERSION-CONTROL to something that is already version-controlled
> is explicitly OK and required behavior).

True. I'll just need to check the code to ensure it Does The Right Thing.

> So that means you will be a fully compliant core versioning server
> (not quite as good as a fully operational death-star, but less
> susceptible to rebel bombing runs :-).  In particular, this should
> give you a non-trivial degree of interoperability in even your 1.0
> server.

Neat :-)

I'll review the core in the 10.11 draft and verify my core support.
Presuming you're going to start a doc on webdav.org for this, then I'll just
post changes as they come up.

It seems like a core server is awfully thin now. And does the
DAV:version-tree report go into the "Version History Option" since it
operates against a version history? And presuming so, the text for this
report should say it "goes to the DAV:version-history of the DAV:target" or
somesuch.

Cheers,
-g

-- 
Greg Stein, http://www.lyra.org/
Received on Friday, 22 December 2000 04:10:54 GMT

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