The interpret trailers command is available as of git v2.2.0, released
Dec 2014.
Make the script +x so one can symlink it from the .git/hooks directory.
Use a shell script rather than Java to test the shell script. The new
script relies on interpret-trailers, making it more reliable. It
generates truly random Change-Ids, making the previous tests with
hard-coded ChangeIds irrelevant.
Test the shell script against /bin/dash too, if available.
Change-Id: Ifc75def19d32b91e196890572f15c4d361fc93fa
68296f7180