do not allow promotion if version is wrong

[#150346407](https://www.pivotaltracker.com/story/show/150346407)

Author: J Evelyn Quintana

ci/pipeline.yml

@@ -203,6 +203,8 @@ jobs:
           passed:
             - bats-centos
             - bats-ubuntu
+      - task: assert-version-aligns
+        file: bosh-linux-stemcell-builder/ci/tasks/assert-version-aligns.yml
       - task: copy-artifacts
         file: bosh-linux-stemcell-builder/ci/tasks/publish.yml
         params:

ci/tasks/assert-version-aligns.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+set -e
+
+export BASE=$(pwd)
+
+semver=`cat ${BASE}/version/number`
+
+pushd "${BASE}/bosh-linux-stemcell-builder"
+  git_branch=`git branch --list -r --contains HEAD | grep -v 'origin/HEAD' | cut -d'/' -f2`
+popd
+
+echo "detected bosh-linux-stemcell-builder will build from branch $git_branch ..."
+
+if [ "$git_branch" = "master" ]; then
+  version_must_match='^[0-9]+\.0\.0$'
+else
+  version_must_match="^${git_branch//x/[0-9]+.0}$"
+  version_must_match="${version_must_match//./\.}"
+fi
+
+echo "will only continue if version to promote matches $version_must_match ..."
+
+if [[ $semver =~ $version_must_match ]]; then
+  echo "version $semver is appropriate for branch $git_branch -- promote will continue"
+  exit 0
+fi
+
+echo "version $semver DOES NOT ALIGN with branch $git_branch -- promotion canceled!"
+
+exit 1
+

ci/tasks/assert-version-aligns.yml

@@ -0,0 +1,16 @@
+---
+platform: linux
+
+image_resource:
+  type: docker-image
+  source:
+    repository: bosh/agent
+
+inputs:
+- name: bosh-linux-stemcell-builder
+- name: version
+
+params: {}
+
+run:
+  path: bosh-linux-stemcell-builder/ci/tasks/assert-version-aligns.sh