fix(data_set): preservation of trailing whitespace

[mattness]

📚 Description

Fixes #497

Problem

data_set was not preserving trailing whitespace in its final argument. For example, data_set "value " or data_set "value " would lose lose one space by the time the test function received the values

Root Cause

The issue occurred in how data_set output was parsed. When using eval "args=($output)" to split the escaped arguments back into an array, bash's word splitting would trim trailing whitespace from the last element because there was nothing after it to delimit where it ended.

Solution

Added an empty string sentinel ('') at the end of data_set output. This ensures there's always something after the last real argument, preventing bash from trimming its trailing whitespace during word splitting.

🔖 Changes

• Modified data_set to append an empty sentinel: printf '%q\n' ""
• Updated runner::parse_data_provider_args to remove the sentinel after parsing
• Added metacharacter detection to safely handle special characters (*, |, &, ;) that could break eval, falling back to character-by-character parsing when needed

✅ To-do list

• I updated the CHANGELOG.md to reflect the new feature or fix

[mattness]

This could be made more succinct with the following, but I chose not to do so in order to minimize what changed.

function data_set() {
  for arg in "${@}"; do
    printf '%q ' "${arg}"
  done
  printf '%q\n' ""  # Sentinel
}

[Chemaclass]

Feel free to work on this refactoring in a follow up PR if you want 🧠

[Chemaclass]

I applied a small fix for compatibility with Bash ^3.2. Thank you!

[mattness]

Bash 3.x got me! Thanks for the fix :)