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

> Christian Couder <christian.couder@gmail.com> writes:
>
>> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
>> ---
>>  t/perf/run | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/t/perf/run b/t/perf/run
>> index 43e4de49ef..bbd703dc4f 100755
>> --- a/t/perf/run
>> +++ b/t/perf/run
>> @@ -105,7 +105,7 @@ get_var_from_env_or_config () {
>>       env_var="$1"
>>       conf_sec="$2"
>>       conf_var="$3"
>> -     # $4 can be set to a default value
>> +     default_value="$4" # optional
>>
>>       # Do nothing if the env variable is already set
>>       eval "test -z \"\${$env_var+x}\"" || return
>> @@ -123,7 +123,7 @@ get_var_from_env_or_config () {
>>       conf_value=$(git config -f "$GIT_PERF_CONFIG_FILE" "$var") &&
>>       eval "$env_var=\"$conf_value\"" && return
>>
>> -     test -n "${4+x}" && eval "$env_var=\"$4\""
>> +     test -n "${default_value+x}" && eval "$env_var=\"$default_value\""
>
> This conversion changes the behaviour.  Because default_value is
> always set by your change in the previous hunk, we end up always
> doing this eval.
>
> The original says "If $4 is set, then ${4+x} becomes x and if $4 is
> not set, ${4+x} is empty, so let's check if ${4+x} is a non-empty
> string to see if $4 is set.  If ${4+x} is a non-empty string, that
> means $4 was set so we do the eval.
>
> 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.