reposync: Avoid multiple downloads of duplicate packages

Download each package only once if it would have been saved to the same
location. This can occur if the repository metadata contains duplicate
entries for the same package.

Resolves: https://issues.redhat.com/browse/RHEL-64320

plugins/reposync.py

@@ -305,7 +305,15 @@ def get_pkglist(self, repo):
             query.filterm(arch='src')
         elif self.opts.arches:
             query.filterm(arch=self.opts.arches)
-        return query
+        # skip packages that would have been downloaded to the same location
+        pkglist = []
+        seen_paths = set()
+        for pkg in query:
+            download_path = self.pkg_download_path(pkg)
+            if download_path not in seen_paths:
+                pkglist.append(pkg)
+                seen_paths.add(download_path)
+        return pkglist
 
     def download_packages(self, pkglist):
         base = self.base