Added description to some Jenkins git mirror pipeline params

Change-Id: I7a252720b18a3c8d2c1b72d9037c5f5c88187b58
diff --git a/jenkins/client/job/git-mirrors/2way.yml b/jenkins/client/job/git-mirrors/2way.yml
index 15f78d7..3b1a62f 100644
--- a/jenkins/client/job/git-mirrors/2way.yml
+++ b/jenkins/client/job/git-mirrors/2way.yml
@@ -52,3 +52,4 @@
               BRANCHES:
                 type: string
                 default: "{{branches}}"
+                description: "Comma-separated list of branches to mirror"
diff --git a/jenkins/client/job/git-mirrors/downstream/init.yml b/jenkins/client/job/git-mirrors/downstream/init.yml
index 649ccdc..6f5a66d 100644
--- a/jenkins/client/job/git-mirrors/downstream/init.yml
+++ b/jenkins/client/job/git-mirrors/downstream/init.yml
@@ -38,3 +38,4 @@
               BRANCHES:
                 type: string
                 default: "{{branches}}"
+                description: "Comma-separated list of branches to mirror"
diff --git a/jenkins/client/job/git-mirrors/upstream/init.yml b/jenkins/client/job/git-mirrors/upstream/init.yml
index 8334f23..1707dca 100644
--- a/jenkins/client/job/git-mirrors/upstream/init.yml
+++ b/jenkins/client/job/git-mirrors/upstream/init.yml
@@ -48,3 +48,4 @@
               BRANCHES:
                 type: string
                 default: "{{branches}}"
+                description: "Comma-separated list of branches to mirror"