add ability to select branch/tag for services and xos core

Change-Id: Icd4e9f7bd2013be167069832c789f7f70b304499
diff --git a/common/Makedefs.branches b/common/Makedefs.branches
new file mode 100644
index 0000000..3522ac4
--- /dev/null
+++ b/common/Makedefs.branches
@@ -0,0 +1,12 @@
+BRANCH=master
+
+XOS_BRANCH=$(BRANCH)
+EXAMPLESERVICE_BRANCH=$(BRANCH)
+OLT_BRANCH=$(BRANCH)
+VSG_BRANCH=$(BRANCH)
+VTN_BRANCH=$(BRANCH)
+VROUTER_BRANCH=$(BRANCH)
+VTR_BRANCH=$(BRANCH)
+ONOS_BRANCH=$(BRANCH)
+FABRIC_BRANCH=$(BRANCH)
+MONITORING_BRANCH=$(BRANCH)