perf: document `perfdirstatedirs`

contrib/perf.py

@@ -1124,6 +1124,8 b' def perfdirstate(ui, repo, **opts):'
 
 @command(b'perfdirstatedirs', formatteropts)
 def perfdirstatedirs(ui, repo, **opts):
+    """benchmap a 'dirstate.hasdir' call from an empty `dirs` cache
+    """
     opts = _byteskwargs(opts)
     timer, fm = gettimer(ui, opts)
     b"a" in repo.dirstate

tests/test-contrib-perf.t

@@ -109,7 +109,7 b' perfstatus'
    perfdirs      (no help text available)
    perfdirstate  benchmap the time necessary to load a dirstate from scratch
    perfdirstatedirs
-                 (no help text available)
+                 benchmap a 'dirstate.hasdir' call from an empty 'dirs' cache
    perfdirstatefoldmap
                  (no help text available)
    perfdirstatewrite