tldr: I propose we use bash explicitly for all diskimage-builder scripts
(at least for the short-term - see details below).
This is something that was raised on my linting changes to enable set -o
pipefail. That is a bash-ism, so it could break in the
diskimage-builder scripts that are run using /bin/sh. Two possible
fixes for that: switch to /bin/bash, or don't use -o pipefail
But I think this raises a bigger question - does diskimage-builder
require bash? If so, I think we should just add a rule to enforce that
/bin/bash is the shell used for everything. I know we have a bunch of
bash-isms in the code already, so at least in the short-term I think
this is probably the way to go, so we can get the benefits of things
like -o pipefail and lose the ambiguity we have right now. For
reference, a quick grep of the diskimage-builder source shows we have
150 scripts using bash explicitly and only 24 that are plain sh, so
making the code truly shell-agnostic is likely to be a significant
amount of work.
In the long run it might be nice to have cross-shell compatibility, but
if we're going to do that I think we need a couple of things: 1) Someone
to do the work (I don't have a particular need to run dib in not-bash,
so I'm not signing up for that :-) 2) Testing in other shells -
obviously just changing /bin/bash to /bin/sh doesn't mean we actually
support anything but bash. We really need to be gating on other shells
if we're going to make a significant effort to support them. It's not
good to ask reviewers to try to catch every bash-ism proposed in a
change. This also relates to some of the unit testing work that is
going on right now too - if we had better unit test coverage of the
scripts we would be able to do this more easily.
Thoughts?
Thanks.
-Ben
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