Add definitions of aptly repos

Change-Id: I85e35f5ebe407388bb15cd3e5ead6ad1948cbdbc
diff --git a/aptly/server/repo/ubuntu/xenial/extra.yml b/aptly/server/repo/ubuntu/xenial/extra.yml
new file mode 100644
index 0000000..2af633f
--- /dev/null
+++ b/aptly/server/repo/ubuntu/xenial/extra.yml
@@ -0,0 +1,15 @@
+parameters:
+  aptly:
+    server:
+      repo:
+        ubuntu-xenial-extra:
+          distribution: xenial
+          component: main
+          architectures: amd64
+          comment: "Extra packages for Ubuntu Xenial"
+          publisher:
+            component: extra
+            distributions:
+              - xenial/nightly
+            architectures:
+              - amd64