extensions: move wrapfilecache function from fsmonitor

extensions: move wrapfilecache function from fsmonitor

It makes more sense to put this in core, so other extensions can
trivially get access to it without having to rely on importing
fsmonitor.

--- a/hgext/fsmonitor/__init__.py	Wed Apr 26 16:05:22 2017 +0200
+++ b/hgext/fsmonitor/__init__.py	Thu Jun 08 10:44:53 2017 -0400
@@ -561,7 +561,8 @@
     return ds
 
 def extsetup(ui):
-    wrapfilecache(localrepo.localrepository, 'dirstate', wrapdirstate)
+    extensions.wrapfilecache(
+        localrepo.localrepository, 'dirstate', wrapdirstate)
     if pycompat.sysplatform == 'darwin':
         # An assist for avoiding the dangling-symlink fsevents bug
         extensions.wrapfunction(os, 'symlink', wrapsymlink)
@@ -709,21 +710,3 @@
                 return overridestatus(orig, self, *args, **kwargs)
 
         repo.__class__ = fsmonitorrepo
-
-def wrapfilecache(cls, propname, wrapper):
-    """Wraps a filecache property. These can't be wrapped using the normal
-    wrapfunction. This should eventually go into upstream Mercurial.
-    """
-    assert callable(wrapper)
-    for currcls in cls.__mro__:
-        if propname in currcls.__dict__:
-            origfn = currcls.__dict__[propname].func
-            assert callable(origfn)
-            def wrap(*args, **kwargs):
-                return wrapper(origfn, *args, **kwargs)
-            currcls.__dict__[propname].func = wrap
-            break
-
-    if currcls is object:
-        raise AttributeError(
-            _("type '%s' has no property '%s'") % (cls, propname))

--- a/mercurial/extensions.py	Wed Apr 26 16:05:22 2017 +0200
+++ b/mercurial/extensions.py	Thu Jun 08 10:44:53 2017 -0400
@@ -308,6 +308,25 @@
     table[key] = tuple(newentry)
     return entry
 
+def wrapfilecache(cls, propname, wrapper):
+    """Wraps a filecache property.
+
+    These can't be wrapped using the normal wrapfunction.
+    """
+    assert callable(wrapper)
+    for currcls in cls.__mro__:
+        if propname in currcls.__dict__:
+            origfn = currcls.__dict__[propname].func
+            assert callable(origfn)
+            def wrap(*args, **kwargs):
+                return wrapper(origfn, *args, **kwargs)
+            currcls.__dict__[propname].func = wrap
+            break
+
+    if currcls is object:
+        raise AttributeError(
+            _("type '%s' has no property '%s'") % (cls, propname))
+
 def wrapfunction(container, funcname, wrapper):
     '''Wrap the function named funcname in container