Re: [PATCH 4/8] perf/run: use $default_value instead of $4

> Junio C Hamano <gitster@pobox.com> writes:
>
>> If you want to be able to use this helper to specify a default value
>> of an empty string (which the orignal that used $4 did), then the
>> previous hunk must be corrected so that it does not unconditionally
>> set default_value to $4.  Perhaps like
>>
>>       if test -n "${4+x}"
>>       then
>>               default_value=$4
>>       else
>>               unset default_value || :
>>       fi
>>
>> or something.
>
> And if you do not care about passing an empty string as the default
> value, then the earlier hunk can stay the same
>
>         default_value=$4
>
> but the eval part should become something like
>
>         test -n "$default_value" && eval ...
>
> Given that you are planning to add yet another optional argument to
> the helper, and when you pass that variable, you'd probably need to
> pass "" as the "default" that is not exported, perhaps this "give up
> ability to pass an empty string as the default" approach may be the
> only thing you could do.