convert: svn: avoid parsing already-seen logentries due to branch following

hgext/convert/subversion.py

@@ -190,7 +190,8 b' class convert_svn(converter_source):'
             parents = []
 
             # branch log might return entries for a parent we already have
-            if rev in self.commits:
+            if (rev in self.commits or
+                (revnum < self.lastrevs.get(self.module, 0))):
                 return
 
             try: