Index: includes/SpecialUndelete.php
===================================================================
--- includes/SpecialUndelete.php	(revision 27816)
+++ includes/SpecialUndelete.php	(working copy)
@@ -522,7 +522,7 @@
  * @addtogroup SpecialPage
  */
 class UndeleteForm {
-	var $mAction, $mTarget, $mTimestamp, $mRestore, $mTargetObj;
+	var $mAction, $mTarget, $mTimestamp, $mRestore, $mInvert, $mTargetObj;
 	var $mTargetTimestamp, $mAllowed, $mComment;
 
 	function UndeleteForm( $request, $par = "" ) {
@@ -537,6 +537,7 @@
 		$posted = $request->wasPosted() &&
 			$wgUser->matchEditToken( $request->getVal( 'wpEditToken' ) );
 		$this->mRestore = $request->getCheck( 'restore' ) && $posted;
+		$this->mInvert = $request->getCheck( 'invert' ) && $posted;
 		$this->mPreview = $request->getCheck( 'preview' ) && $posted;
 		$this->mDiff = $request->getCheck( 'diff' );
 		$this->mComment = $request->getText( 'wpComment' );
@@ -556,7 +557,7 @@
 		} else {
 			$this->mTargetObj = NULL;
 		}
-		if( $this->mRestore ) {
+		if( $this->mRestore || $this->mInvert ) {
 			$timestamps = array();
 			$this->mFileVersions = array();
 			foreach( $_REQUEST as $key => $val ) {
@@ -602,6 +603,9 @@
 		if( $this->mRestore && $this->mAction == "submit" ) {
 			return $this->undelete();
 		}
+		if( $this->mInvert && $this->mAction == "submit" ) {
+			return $this->showHistory( $this->mTargetTimestamp );
+		}
 		return $this->showHistory();
 	}
 
@@ -821,7 +825,7 @@
 		$store->stream( $key );
 	}
 
-	/* private */ function showHistory() {
+	/* private */ function showHistory( $selectedTimeStamps = Array () ) {
 		global $wgLang, $wgContLang, $wgUser, $wgOut;
 
 		$sk = $wgUser->getSkin();
@@ -918,6 +922,7 @@
 						<td>&nbsp;</td>
 						<td>" .
 							Xml::submitButton( wfMsg( 'undeletebtn' ), array( 'name' => 'restore', 'id' => 'mw-undelete-submit' ) ) .
+							Xml::submitButton( wfMsg( 'undeleteinvert' ), array( 'name' => 'invert', 'id' => 'mw-undelete-invert' ) ) .
 							Xml::element( 'input', array( 'type' => 'reset', 'value' => wfMsg( 'undeletereset' ), 'id' => 'mw-undelete-reset' ) ) .
 						"</td>
 					</tr>" .
@@ -940,7 +945,16 @@
 				$remaining--;
 				$ts = wfTimestamp( TS_MW, $row->ar_timestamp );
 				if ( $this->mAllowed ) {
-					$checkBox = Xml::check( "ts$ts" );
+					if ( sizeof($selectedTimeStamps) > 0 ) {
+						if ( in_array( $ts, $selectedTimeStamps ) ){
+							$checkBox = Xml::check( "ts$ts" );
+						} else {
+							$checkBox = Xml::check( "ts$ts", true );
+						}
+						
+					} else {
+						$checkBox = Xml::check( "ts$ts" );
+					}
 					$pageLink = $sk->makeKnownLinkObj( $titleObj,
 						$wgLang->timeanddate( $ts, true ),
 						"target=$target&timestamp=$ts" );
Index: languages/messages/MessagesEn.php
===================================================================
--- languages/messages/MessagesEn.php	(revision 27816)
+++ languages/messages/MessagesEn.php	(working copy)
@@ -1950,6 +1950,7 @@
 revision may have been restored or removed from the archive.',
 'undelete-nodiff'          => 'No previous revision found.',
 'undeletebtn'              => 'Restore',
+'undeleteinvert'           => 'Invert selection',
 'undeletereset'            => 'Reset',
 'undeletecomment'          => 'Comment:',
 'undeletedarticle'         => 'restored "[[$1]]"',
Index: maintenance/language/messages.inc
===================================================================
--- maintenance/language/messages.inc	(revision 27816)
+++ maintenance/language/messages.inc	(working copy)
@@ -1272,6 +1272,7 @@
 		'undeleterevision-missing',
 		'undelete-nodiff',
 		'undeletebtn',
+		'undeleteinvert',
 		'undeletereset',
 		'undeletecomment',
 		'undeletedarticle',