Deprecate proc kwarg to call_historic()

It's a bad name, use `result_callback` instead.

Resolves pytest-dev#120

pluggy/hooks.py

@@ -257,20 +257,32 @@ def __call__(self, *args, **kwargs):
                 )
         return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
 
-    def call_historic(self, proc=None, kwargs=None):
-        """ call the hook with given ``kwargs`` for all registered plugins and
+    def call_historic(self, result_callback=None, kwargs=None, proc=None):
+        """Call the hook with given ``kwargs`` for all registered plugins and
         for all plugins which will be registered afterwards.
 
-        If ``proc`` is not None it will be called for for each non-None result
-        obtained from a hook implementation.
+        If ``result_callback`` is not ``None`` it will be called for for each
+        non-None result obtained from a hook implementation.
+
+        .. note::
+            The ``proc`` argument is now deprecated.
         """
-        self._call_history.append((kwargs or {}, proc))
+        if proc is not None:
+            warnings.warn(
+                "Support for `proc` argument is now deprecated and will be"
+                "removed in an upcoming release.",
+                DeprecationWarning
+            )
+            result_callback = proc
+
+        self._call_history.append((kwargs or {}, result_callback))
         # historizing hooks don't return results
         res = self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
-        if proc is None:
+        if result_callback is None:
             return
+        # XXX: remember firstresult isn't compat with historic
         for x in res or []:
-            proc(x)
+            result_callback(x)
 
     def call_extra(self, methods, kwargs):
         """ Call the hook with some additional temporarily participating

testing/test_pluginmanager.py

@@ -217,7 +217,7 @@ def he_method1(self, arg):
     pm.register(Plugin1())
 
     he_method1 = pm.hook.he_method1
-    he_method1.call_historic(proc=callback, kwargs=dict(arg=1))
+    he_method1.call_historic(result_callback=callback, kwargs=dict(arg=1))
 
     class Plugin2(object):
         @hookimpl
@@ -399,3 +399,20 @@ def example_hook():
     assert getattr(pm.hook, 'example_hook', None)  # conftest.example_hook should be collected
     assert pm.parse_hookimpl_opts(conftest, 'example_blah') is None
     assert pm.parse_hookimpl_opts(conftest, 'example_hook') == {}
+
+
+def test_callhistoric_proc_deprecated(pm):
+    """``proc`` kwarg to `PluginMananger.call_historic()` is now officially
+    deprecated.
+    """
+    class P1(object):
+        @hookspec(historic=True)
+        @hookimpl
+        def m(self, x):
+            pass
+
+    p1 = P1()
+    pm.add_hookspecs(p1)
+    pm.register(p1)
+    with pytest.deprecated_call():
+        pm.hook.m.call_historic(kwargs=dict(x=10), proc=lambda res: res)