github-pull-request-number.user.js

// ==UserScript==
// @name GitHub - Show pull request numbers
// @match https://github.com/*/*/pulls
// @match https://github.com/*/*/pulls/*
// ==/UserScript==

[].slice.call( document.querySelectorAll( ".listings h3" ) ).forEach(function( elem ) {
	var anchor = elem.getElementsByTagName( "a" )[ 0 ],
		id = anchor.href.match( /(\d+)$/ )[ 0 ],
		span = document.createElement( "span" ),
		tracNum = anchor.innerHTML.match( /#(\d+)/ ),
		spanHTML;
	if( tracNum ) {
		spanHTML = document.createElement( "a" );
		spanHTML.href = "http://bugs.jqueryui.com/ticket/" + tracNum[0].substr( 1 );
		spanHTML.target = "_blank";
		spanHTML.style.color = "#F00";
		spanHTML.innerHTML = id + ": ";
		span.appendChild( spanHTML );
		anchor.parentNode.insertBefore( span, anchor );
	} else {
		span.innerHTML = id + ": ";
		anchor.insertBefore( span, anchor.childNodes[0] );
	}
});