tests: show the pattern generated for a relative glob

Differential Revision: https://phab.mercurial-scm.org/D6763

tests/test-hgignore.t

@@ -176,6 +176,8 b' Test relative ignore path (issue4473):'
   ? .hgignore
   ? a.c
   ? syntax
+  $ hg debugignore
+  <includematcher includes='(?:|.*/)[^/]*\\.o(?:/|$)'>
 
   $ cd ..
   $ echo > .hg/testhgignorerel