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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Autoversioning</title><link rel="stylesheet" href="styles.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><link rel="start" href="index.html" title="Version Control with Subversion" /><link rel="up" href="svn.webdav.html" title="Appendix C. WebDAV and Autoversioning" /><link rel="prev" href="svn.webdav.basic.html" title="What is WebDAV?" /><link rel="next" href="svn.webdav.clients.html" title="Client Interoperability" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Autoversioning</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="svn.webdav.basic.html">Prev</a> </td><th width="60%" align="center">Appendix C. WebDAV and Autoversioning</th><td width="20%" align="right"> <a accesskey="n" href="svn.webdav.clients.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="svn.webdav.autoversioning"></a>Autoversioning</h2></div></div></div><p>While the Subversion client is not a full DeltaV client, nor
the Subversion server a full DeltaV server, there's still a
glimmer of WebDAV interoperability to be happy about: it's
called autoversioning.</p><p>Autoversioning is an optional feature defined in the DeltaV
standard. A typical DeltaV server will reject an ignorant
WebDAV client attempting to do a <code class="literal">PUT</code> to a
file that's under version control. To change a
version-controlled file, the server expects a series of proper
versioning requests: something like
<code class="literal">MKACTIVITY</code>, <code class="literal">CHECKOUT</code>,
<code class="literal">PUT</code>, <code class="literal">CHECKIN</code>. But if the
DeltaV server supports autoversioning, then write-requests from
basic WebDAV clients are accepted. The server behaves as if the
client <span class="emphasis"><em>had</em></span> issued the proper series of
versioning requests, performing a commit under the hood. In
other words, it allows a DeltaV server to interoperate with
ordinary WebDAV clients that don't understand versioning.</p><p>Because so many operating systems already have integrated
WebDAV clients, the use case for this feature can be incredibly
appealing to administrators working with non-technical users:
imagine an office of ordinary users running Microsoft Windows or
Mac OS. Each user “<span class="quote">mounts</span>” the Subversion
repository, which appears to be an ordinary network folder.
They use the shared folder as they always do: open files, edit
them, save them. Meanwhile, the server is automatically
versioning everything. Any administrator (or knowledgeable
user) can still use a Subversion client to search history and
retrieve older versions of data.</p><p>This scenario isn't fiction: it's real and it works, as of
Subversion 1.2 and later. To activate autoversioning in
<span class="command"><strong>mod_dav_svn</strong></span>, use
the <code class="literal">SVNAutoversioning</code> directive within
the <code class="filename">httpd.conf</code> Location block, like
so:</p><pre class="screen">
<Location /repos>
DAV svn
SVNPath /var/svn/repository
SVNAutoversioning on
</Location>
</pre><p>When SVNAutoversioning is active, write requests from WebDAV
clients result in automatic commits. A generic log message is
auto-generated and attached to each revision.</p><p>Before activating this feature, however, understand what
you're getting into. WebDAV clients tend to do
<span class="emphasis"><em>many</em></span> write requests, resulting in a huge
number of automatically committed revisions. For example, when
saving data, many clients will do a <code class="literal">PUT</code> of a
0-byte file (as a way of reserving a name) followed by another
<code class="literal">PUT</code> with the real file data. The single
file-write results in two separate commits. Also consider that
many applications auto-save every few minutes, resulting in even
more commits.</p><p>If you have a post-commit hook program that sends email, you
may want to disable email generation either altogether, or on
certain sections of the repository; it depends on whether you
think the influx of emails will still prove to be valuable
notifications or not. Also, a smart post-commit hook program
can distinguish between a transaction created via autoversioning
and one created through a normal <span class="command"><strong>svn commit</strong></span>.
The trick is to look for a revision property
named <code class="literal">svn:autoversioned</code>. If present, the
commit was made by a generic WebDAV client.</p><p>Another feature that may be a useful complement
for <code class="literal">SVNAutoversioning</code> comes from
Apache's <code class="literal">mod_mime</code> module. If a WebDAV client
adds a new file to the repository, there's no opportunity for
the user to set the the <code class="literal">svn:mime-type</code>
property. This might cause the file to appear as generic icon
when viewed within a WebDAV shared folder, not having an
association with any application. One remedy is to have a
sysadmin (or other Subversion-knowledgeable person) check out a
working copy and manually set
the <code class="literal">svn:mime-type</code> property on necessary
files. But there's potentially no end to such cleanup tasks.
Instead, you can use the <code class="literal">ModMimeUsePathInfo</code>
directive in your Subversion <code class="literal"><Location></code>
block:</p><pre class="screen">
<Location /repos>
DAV svn
SVNPath /var/svn/repository
SVNAutoversioning on
ModMimeUsePathInfo on
</Location>
</pre><p>This directive allows <code class="literal">mod_mime</code> to attempt
automatic deduction of the mime-type on new files that enter the
repository via autoversioning. The module looks at the file's
named extension and possibly the contents as well; if the file
matches some common patterns, then the the
file's <code class="literal">svn:mime-type</code> property will be set
automatically.</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="svn.webdav.basic.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="svn.webdav.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="svn.webdav.clients.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">What is WebDAV? </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Client Interoperability</td></tr></table></div></body></html>
