Is your feature request related to a problem? Please describe.
#2144 identified a use of bash features in a sh script, which escaped our notice in testing.

Describe the solution you'd like
We should run our shell scripts in a more diverse set of environments (in particular, finding environments where sh is not aliased to bash).

Describe alternatives you've considered
Alternatively, we could just rewrite our hashbangs to /bin/bash.

Additional context
N/A.