ci: Add a commit validation entrypoint

.cci.jenkinsfile

@@ -30,11 +30,9 @@ codestyle: {
   cosaPod(buildroot: true) {
       checkout scm
       shwrap("""
-        # Jenkins by default only fetches the branch it's testing. Explicitly fetch master
-        # for ci-commitmessage-submodules.sh
+        # Ensures that we get refs to aid `git describe`
         git fetch origin +refs/heads/master:refs/remotes/origin/master
-        ci/ci-commitmessage-submodules.sh
-        ci/codestyle.sh
+        ci/commit-validation.sh
       """)
   }
 },

ci/commit-validation.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+set -xeuo pipefail
+# Add cheap (non-building) checks here
+dn=$(dirname $0)
+${dn}/codestyle.sh
+${dn}/ci-commitmessage-submodules.sh