Update action to use yb_release_train variable.

.github/workflows/update-version.yaml

@@ -3,8 +3,6 @@ on:
   repository_dispatch:
     types:
     - update-on-release
-env:
-  CURRENT_STABLE: 2.3
 jobs:
   update-version:
     if: github.event.client_payload.prerelease == 'false'
@@ -34,14 +32,11 @@ jobs:
         echo "Extracted the version number '${version_number}'."
         echo "::set-output name=yb_version::${version_number}"
     - name: "Switch to correct branch"
-      id: extract-branch
+      id: switch-branch
       run: |
-        rel=${{steps.extract-version.outputs.yb_version}}
-        a=( ${rel//./ } )
-        branch_name="${a[0]}.${a[1]}"
-        if [[ "${branch_name}" == "${CURRENT_STABLE}" ]]; then # 2.3 is the latest "master" release
-          branch_name='master'
-        fi
+        # We use the yb_release_train as the branch in this repo
+        # This allows us to map multiple '2.2' release branches to a single set of helm charts
+        branch_name="${{github.events.client_payload.yb_release_train}}"
         if git branch | grep -qE "^${branch_name}$"; then
           # branch already exists so check it out
           git checkout ${branch_name}