title: How to use subversion's propset against a URL?
body: <p>Is it possible to manipulate a subversion property such as <code>svn:externals</code> via a URL only?  (i.e. without having a working copy.)</p>
  
  <p>I'd like a script that pins <code>svn:externals</code> to a particular revision given a subversion URL, but this seems to be impossible:</p>
  
  <pre><code>$ svn propset foo bar https://example.com/svn/myproject/trunk
  svn: Setting property on non-local target 'https://example.com/svn/myproject/trunk' needs a base revision
  
  $ svn propset foo bar -r HEAD https://example.com/svn/myproject/trunk
  svn: Try 'svn help' for more info
  svn: Cannot specify revision for setting versioned property 'foo'
  
  $ svn propset foo bar --revprop -r HEAD https://example.com/svn/myproject/trunk
  svn: DAV request failed; it's possible that the repository's pre-revprop-change hook either failed or is non-existent
  svn: At least one property change failed; repository is unchanged
  svn: Error setting property 'foo': 
  could not remove a property
  </code></pre>
  
  <p>(I get the same results if I use an actual revision number instead of <code>HEAD</code> as well.)</p>