Print some more information at the beginning (#311)

In particular, the show of HEAD^2 and HEAD^1 should ensure that both parents of the merge commit are printed.
12 files changed
tree: ea2ae90682131081b51e1af4b5d5ff839d45ecc9
  1. abi/
  2. bin/
  3. docker/
  4. jenkins/
  5. README.md
README.md

trafficserver-ci