Re: [PATCH v5 5/6] check-whitespace: detect if no base_commit is provided

> Karthik Nayak <karthik.188@gmail.com> writes:
>
>> +    - |
>> +      R=${CI_MERGE_REQUEST_TARGET_BRANCH_SHA-${CI_MERGE_REQUEST_DIFF_BASE_SHA?}}
>> +
>> +      if test -z "$R"
>> +      then
>> +        echo "CI_MERGE_REQUEST_DIFF_BASE_SHA should always exist!"
>> +        exit 1
>> +      fi
>
> The same comment applies as the previous step.
>
> 	R=${A-${B:?}} || exit
>
> should be sufficient.
>
> A demonstration.
>
>         $ unset A; unset B; C=${A-${B:?}} && echo "C=$C"
>         bash: B: parameter null or not set
>         $ A=a; unset B; C=${A-${B:?}} && echo "C=$C"
>         C=a
>         $ unset A; B=; C=${A-${B:?}} && echo "C=$C"
>         bash: B: parameter null or not set
>         $ unset A; B=b; C=${A-${B:?}} && echo "C=$C"
>         C=b
>         $ A=a; B=b; C=${A-${B:?}} && echo "C=$C"
>         C=a
>
> Note that the broken case we do not see C=<value> becaues the
> assignment fails with non-zero status.
>
> Thanks.