perf: document `perfdirstate`

contrib/perf.py

@@ -1103,6 +1103,11 b' def perfdirs(ui, repo, **opts):'
 
 @command(b'perfdirstate', formatteropts)
 def perfdirstate(ui, repo, **opts):
+    """benchmap the time necessary to load a dirstate from scratch
+
+    The dirstate is loaded to the point were a "contains" request can be
+    answered.
+    """
     opts = _byteskwargs(opts)
     timer, fm = gettimer(ui, opts)
     b"a" in repo.dirstate

tests/test-contrib-perf.t

@@ -107,7 +107,7 b' perfstatus'
    perfdirfoldmap
                  (no help text available)
    perfdirs      (no help text available)
-   perfdirstate  (no help text available)
+   perfdirstate  benchmap the time necessary to load a dirstate from scratch
    perfdirstatedirs
                  (no help text available)
    perfdirstatefoldmap