t/40-commit: set -o pipefail, as well as -e

We don't actually need this at the moment, but best it's there
in case someone uses a pipe without thinking to add this.

Author: 0cjs

t/40-commit.t

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 . t/test-lib.sh
-set -e
+set -e -o 'pipefail'
 
 echo "1..9"