A bookmarklet which brings you directly from a wordpress.org plugin page to the svn repository on plugins.svn.wordpress.org.

bookmarklet.js

(function(){var b=document.location.href,a=document.createElement('a'),path=[],protocol='http';a.href=b;path=a.pathname.split('/');if('https:'==a.protocol){protocol='https'}if('wordpress.org'!=a.hostname||'undefined'==typeof path[1]||''==path[1]||'plugins'!=path[1]||'undefined'==typeof path[2]||''==path[2]){alert('It seems you are not facing a wordpress plugin page. The URL must match: worpress.org/plugins/{PLUGIN_NAME}');return}document.location.href=protocol+'://plugins.svn.wordpress.org/'+path[2]+'/trunk/'})();

source.js

( function() {
	var 
		url = document.location.href, 
		a = document.createElement( 'a' ),
		path = [],
		protocol = 'http';
		
		a.href = url;
		path = a.pathname.split( '/' );
		if ( 'https:' == a.protocol ) {
			protocol = 'https';
		}
		if ( 
			 'wordpress.org' != a.hostname 
		  || 'undefined' == typeof path[ 1 ] || '' == path[ 1 ] || 'plugins' != path[ 1 ]
		  || 'undefined' == typeof path[ 2 ] || '' == path[ 2 ]
		) {
			alert( 'It seems you are not facing a wordpress plugin page. The URL must match: worpress.org/plugins/{PLUGIN_NAME}' );
			
			return;
		} 
		document.location.href = protocol + '://plugins.svn.wordpress.org/' + path[ 2 ] + '/trunk/';
		
} )();