Confirming that lint-staged has an issue working with git add -p, verified as follows:

• Edited index.js to make two changes:
  • Rename req and res to request and response
  • Change port from 3000 to 5000
• Ran git add -p to split to two hunks
• Ran git commit -m "<MSG>" to add first hunk to commit msg, which ran lint-staged and prettier
• Notice that both hunks were added, and unstaged changes are also part of commit