Add files to pre-commit?

Question

git

Hello, please tell me how to add a file in the pre-commit hook.
In file ./.git/hooks/pre-commit

#!/bin/sh
openssl aes-256-cbc -k "1" -in .env -out .env.enc
git add .env.enc

Next always when I change the .env file and create a commit git commit -am 'a'

$ git commit -am 'a'
git commit -am 'a'
*** WARNING : deprecated key derivation used.
Using -iter or -pbkdf2 would be better.
On branch master
Your branch is ahead of 'origin/master' by 35 commits.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean

Only after a re-commit changes are already saved. How to fix it? Thank you.