Trigger CDC schema tests if a migration is present

If a migration is present in the commit, this triggers
a build that checks if the migration will break things
for CDC/Canvas Data 2.

test plan:
- Verify that, if a migration adds a new column, the
  CDC Schema Check step fails in the build (like in
  build 4636, a previous version of this commit which
  had a migration added)
- If a migration renames a column that CDC doesn't
  care about, the CDC Schema Check step runs but
  does not fail.
- If a commit has no migration in it, the CDC Schema
  Check step doesn't run.

Change-Id: Ibe33955d11ef62bf68b8dd4cdb838cf2dad126e8
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/240916
Reviewed-by: James Butters <jbutters@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Tucker Mcknight <tmcknight@instructure.com>
Product-Review: Tucker Mcknight <tmcknight@instructure.com>

Jenkinsfile

@@ -347,6 +347,18 @@ pipeline {
                 }
               }
 
+              if (sh(script: 'build/new-jenkins/check-for-migrations.sh', returnStatus: true) == 0) {
+                echo 'adding CDC Schema check'
+                stages['CDC Schema Check'] = {
+                  build job: '../Canvas/cdc-event-transformer-master', parameters: [
+                    string(name: 'CANVAS_LMS_IMAGE_TAG', value: "${env.NAME}-${env.TAG_SUFFIX}")
+                  ]
+                }
+              }
+              else {
+                echo 'no migrations added, skipping CDC Schema check'
+              }
+
               if (env.GERRIT_EVENT_TYPE != 'change-merged' && (sh(script: 'build/new-jenkins/spec-changes.sh', returnStatus: true) == 0)) {
                 echo 'adding Flakey Spec Catcher'
                 stages['Flakey Spec Catcher'] = {

build/new-jenkins/check-for-migrations.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# grep will exit with code 0 if any commits between origin/master and
+# HEAD contain db/migrate.
+git show --pretty="" --name-only origin/master..HEAD | grep "db/migrate"