Adjusted regex to make more accurate

pre-commit

#!/bin/sh

if git rev-parse --verify HEAD >/dev/null 2>&1
then
    against=HEAD
else
    # Initial commit: diff against an empty tree object
    against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

# Redirect output to stderr.
exec 1>&2

# Check changed files for an AWS keys
KEY_ID=$(git diff --cached --name-only -z $against | xargs -0 cat | grep -cEIw '[A-Z0-9]{20}')
KEY=$(git diff --cached --name-only -z $against | xargs -0 cat | grep -cEI '[^A-Za-z0-9/+][A-Za-z0-9/+=]{40}([^A-Za-z0-9/+=]|$)')

if [ $KEY_ID -ne 0 -a $KEY -ne 0 ]; then
    echo "Found patterns for AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY"
    echo "Please check your code and remove API keys."
    exit 1
fi

# Normal exit
exit 0