diff -up createrepo-0.9.9/createrepo/merge.py.old createrepo-0.9.9/createrepo/merge.py
--- createrepo-0.9.9/createrepo/merge.py.old	2015-12-08 11:08:51.998837759 +0100
+++ createrepo-0.9.9/createrepo/merge.py	2015-12-08 11:09:58.868951847 +0100
@@ -70,9 +70,7 @@ class RepoMergeBase:
 
         for repo in repos:
             for pkg in repo.sack:
-                others = self.yumbase.pkgSack.searchNevra(name=pkg.name, arch=pkg.arch)
-                # NOTE the above is definitely going to catch other versions which may
-                # be an invalid comparison
+                others = self.yumbase.pkgSack.searchNevra(pkg.name, pkg.epoch, pkg.version, pkg.release, pkg.arch)
                 if len(others) > 1:
                     for thatpkg in others:
                         if pkg.repoid == thatpkg.repoid: continue
commit b8904f59773a478aedd416963ec451c678a6bb72
Author: Zdenek Pavlas <zpavlas@redhat.com>
Date:   Wed Jan 29 09:53:37 2014 +0100

    Support API users that set pkglist=<package sack>. BZ 1058975
    
    Commit 84a237f6a2e661879147e1ee5f9a2be984267991
    broke this use case. Make it work again.

diff --git a/createrepo/__init__.py b/createrepo/__init__.py
index b1875f6..85f2a3d 100644
--- a/createrepo/__init__.py
+++ b/createrepo/__init__.py
@@ -400,7 +400,9 @@ class MetaDataGenerator:
         if self.conf.update:
             self._setup_old_metadata_lookup()
         # rpms we're going to be dealing with
-        if self.conf.pkglist:
+        if isinstance(self.conf.pkglist, MetaSack):
+            packages = self.conf.pkglist
+        elif self.conf.pkglist:
             packages = []
             for pkg in self.conf.pkglist:
                 if '://' in pkg: # remote