revset: use try-except instead of if-else because of perf

For wdir(), we now raises an exception which will be raised when wdir() will be
passed, so catching that exception is better checking for wdir() using if-else.

mercurial/revset.py

@@ -1456,10 +1456,10 b' def parents(repo, subset, x):'
         up = ps.update
         parentrevs = cl.parentrevs
         for r in getset(repo, fullreposet(repo), x):
-            if r == node.wdirrev:
+            try:
+                up(parentrevs(r))
+            except error.WdirUnsupported:
                 up(p.rev() for p in repo[r].parents())
-            else:
-                up(parentrevs(r))
     ps -= {node.nullrev}
     return subset & ps