HOTFIX: Set fetch-depth to 0 for the phpstan check

[AdamJHall]

Description of the proposed changes
Currently the phpstan check is failing silently as it cannot get a diff of what files have changed. This along with an updated script in the repo should allow phpstan to start working again in github.

#!/bin/bash

# Detect environment and get changed PHP files accordingly
if [ "${GITHUB_ACTIONS}" = "true" ]; then
    # CI: diff against PR base branch
    BASE_REF="${GITHUB_BASE_REF:-production}"
    git fetch origin "$BASE_REF" --depth=1
    PHP_FILES=$(git diff --name-only --diff-filter=AM "origin/${BASE_REF}...HEAD" -- '*.php' '*.phtml')
else
    # Local pre-commit hook (cghooks): diff against staged index
    PHP_FILES=$(git diff --name-only --cached --diff-filter=AM -- '*.php' '*.phtml')
fi

if [[ -z "$PHP_FILES" ]]; then
    echo "Nothing to analyse"
else
    ./vendor/bin/phpstan analyse -c php.neon $PHP_FILES
fi

Notes to reviewers

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