gitweb: Fix tree link associated with each commit log entry.

The link forgot to have hb parameter and the resulting tree view
failed to show the navbar for that commit.

Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -2871,7 +2871,7 @@ sub git_log {
 		      " | " .
 		      $cgi->a({-href => href(action=>"commitdiff", hash=>$commit)}, "commitdiff") .
 		      " | " .
-		      $cgi->a({-href => href(action=>"tree", hash=>$commit), hash_base=>$commit}, "tree") .
+		      $cgi->a({-href => href(action=>"tree", hash=>$commit, hash_base=>$commit)}, "tree") .
 		      "<br/>\n" .
 		      "</div>\n" .
 		      "<i>" . esc_html($co{'author_name'}) .  " [$ad{'rfc2822'}]</i><br/>\n" .