changeset 24404:96cccf1e3257

treemanifest: make diff() faster

Containment checking is slower in treemanifest than it is in
manifestdict, making the current diff algorithm O(n log n). By
traversing both treemanifests in parallel, we can make it O(n). More
importantly, once we start lazily loading submanifests, we will be
able to easily skip entire submanifest if they have the same nodeid.

--- a/mercurial/manifest.py	Mon Feb 23 10:57:57 2015 -0800
+++ b/mercurial/manifest.py	Thu Feb 19 17:13:35 2015 -0800
@@ -527,25 +527,33 @@
         the nodeid will be None and the flags will be the empty
         string.
         '''
-        diff = {}
+        result = {}
+        emptytree = treemanifest()
+        def _diff(t1, t2):
+            for d, m1 in t1._dirs.iteritems():
+                m2 = t2._dirs.get(d, emptytree)
+                _diff(m1, m2)
+
+            for d, m2 in t2._dirs.iteritems():
+                if d not in t1._dirs:
+                    _diff(emptytree, m2)
 
-        for fn, n1 in self.iteritems():
-            fl1 = self.flags(fn)
-            n2 = m2.get(fn, None)
-            fl2 = m2.flags(fn)
-            if n2 is None:
-                fl2 = ''
-            if n1 != n2 or fl1 != fl2:
-                diff[fn] = ((n1, fl1), (n2, fl2))
-            elif clean:
-                diff[fn] = None
+            for fn, n1 in t1._files.iteritems():
+                fl1 = t1._flags.get(fn, '')
+                n2 = t2._files.get(fn, None)
+                fl2 = t2._flags.get(fn, '')
+                if n1 != n2 or fl1 != fl2:
+                    result[t1._subpath(fn)] = ((n1, fl1), (n2, fl2))
+                elif clean:
+                    result[t1._subpath(fn)] = None
 
-        for fn, n2 in m2.iteritems():
-            if fn not in self:
-                fl2 = m2.flags(fn)
-                diff[fn] = ((None, ''), (n2, fl2))
+            for fn, n2 in t2._files.iteritems():
+                if fn not in t1._files:
+                    fl2 = t2._flags.get(fn, '')
+                    result[t2._subpath(fn)] = ((None, ''), (n2, fl2))
 
-        return diff
+        _diff(self, m2)
+        return result
 
     def text(self):
         """Get the full data of this manifest as a bytestring."""