perf: replace ui.configint() by getint() for Mercurial earlier than 1.9

Before this patch, using ui.configint() prevents perf.py from
measuring performance with Mercurial earlier than 1.9 (or
fa2b596db182), because ui.configint() isn't available in such
Mercurial, even though there are some code paths for Mercurial earlier
than 1.9 in perf.py.

For example, setting "_prereadsize" attribute in perfindex() and
perfnodelookup() is effective only with hg earlier than 1.8 (or
61c9bc3da402).

This patch replaces ui.configint() invocations by newly introduced
getint().

This patch also adds check-perf-code.py an extra check entry to detect
direct usage of ui.configint() in perf.py.

BTW, this patch doesn't choose adding configint() method at runtime by
replacing ui.__class__ like below, even though this is the recommended
way to modern Mercurial extensions.

    def uisetup(ui):
        if not util.safehasattr(ui, 'configint'):
            class uiwrap(ui.__class__):
                def configint(self, section, name, ....):
                    ....
            ui.__class__ = uiwrap

Because changes to ui.__class__ by uisetup() of loaded extension have
been propagated since 1.6.1 (or d8d0fc3988ca), the recommended way
above doesn't work as expected with Mercurial earlier than it.

contrib/perf.py

@@ -131,7 +131,7 b' def gettimer(ui, opts=None):'
 
     # enforce an idle period before execution to counteract power management
     # experimental config: perf.presleep
-    time.sleep(ui.configint("perf", "presleep", 1))
+    time.sleep(getint(ui, "perf", "presleep", 1))
 
     if opts is None:
         opts = {}
@@ -222,6 +222,18 b' def _timer(fm, func, title=None):'
 
 # utilities for historical portability
 
+def getint(ui, section, name, default):
+    # for "historical portability":
+    # ui.configint has been available since 1.9 (or fa2b596db182)
+    v = ui.config(section, name, None)
+    if v is None:
+        return default
+    try:
+        return int(v)
+    except ValueError:
+        raise error.ConfigError(("%s.%s is not an integer ('%s')")
+                                % (section, name, v))
+
 def safeattrsetter(obj, name, ignoremissing=False):
     """Ensure that 'obj' has 'name' attribute before subsequent setattr
 
@@ -569,7 +581,7 b' def perfparents(ui, repo, **opts):'
     timer, fm = gettimer(ui, opts)
     # control the number of commits perfparents iterates over
     # experimental config: perf.parentscount
-    count = ui.configint("perf", "parentscount", 1000)
+    count = getint(ui, "perf", "parentscount", 1000)
     if len(repo.changelog) < count:
         raise error.Abort("repo needs %d commits for this test" % count)
     repo = repo.unfiltered()

tests/check-perf-code.py

@@ -14,6 +14,8 b' perfpypats = ['
      "use getbranchmapsubsettable() for early Mercurial"),
     (r'\.(vfs|svfs|opener|sopener)',
      "use getvfs()/getsvfs() for early Mercurial"),
+    (r'ui\.configint',
+     "use getint() instead of ui.configint() for early Mercurial"),
   ],
   # warnings
   [