perf: introduce a `--iteration` to `perfdirstate`

This flag benchmark an iteration over all the file in the dirstate. This
will be useful to compare the Python and the Rust implementation of the
dirstate.

contrib/perf.py

@@ -1101,10 +1101,14 b' def perfdirs(ui, repo, **opts):'
     fm.end()
 
 
-@command(b'perfdirstate', formatteropts)
+@command(b'perfdirstate', [
+            (b'', b'iteration', None,
+             b'benchmark a full iteration for the dirstate'),
+        ] + formatteropts)
 def perfdirstate(ui, repo, **opts):
-    """benchmap the time necessary to load a dirstate from scratch
-
+    """benchmap the time of various distate operations
+
+    By default benchmark the time necessary to load a dirstate from scratch.
     The dirstate is loaded to the point were a "contains" request can be
     answered.
     """
@@ -1112,11 +1116,18 b' def perfdirstate(ui, repo, **opts):'
     timer, fm = gettimer(ui, opts)
     b"a" in repo.dirstate
 
-    def setup():
-        repo.dirstate.invalidate()
-
-    def d():
-        b"a" in repo.dirstate
+    if opts[b'iteration']:
+        setup = None
+        dirstate = repo.dirstate
+        def d():
+            for f in dirstate:
+                pass
+    else:
+        def setup():
+            repo.dirstate.invalidate()
+
+        def d():
+            b"a" in repo.dirstate
 
     timer(d, setup=setup)
     fm.end()

tests/test-contrib-perf.t

@@ -107,7 +107,7 b' perfstatus'
    perfdirfoldmap
                  benchmap a 'dirstate._map.dirfoldmap.get()' request
    perfdirs      (no help text available)
-   perfdirstate  benchmap the time necessary to load a dirstate from scratch
+   perfdirstate  benchmap the time of various distate operations
    perfdirstatedirs
                  benchmap a 'dirstate.hasdir' call from an empty 'dirs' cache
    perfdirstatefoldmap
@@ -205,6 +205,7 b' perfstatus'
   $ hg perfdirfoldmap
   $ hg perfdirs
   $ hg perfdirstate
+  $ hg perfdirstate --iteration
   $ hg perfdirstatedirs
   $ hg perfdirstatefoldmap
   $ hg perfdirstatewrite