Be explicit and verbose when using git diff.
Be explicit and verbose when using git diff.

Specify that git should diff against HEAD when diffing in the
propose_requirements_update.sh script. Replace --quiet with --exit-code
so that we can verbosely see what differences there are.

Change-Id: I0d194151db457f7eb56e010c94b20562d0221e34

open-switch/infra_puppet-jenkins,open-switch/infra_puppet-jenkins