#!/usr/bin/env bash
# ============================================================================
# PRE-MERGE-COMMIT HOOK: Run pre-commit checks on auto-created merge commits
# ============================================================================
# Triggered by: `git merge` when git AUTO-CREATES a merge commit (i.e. the
# merge succeeded without conflicts and there is nothing for the user to
# resolve manually). In that case git does NOT fire pre-commit — this hook
# is its substitute.
#
# SCOPE — what this hook DOES cover:
#   - Non-fast-forward merge where the combined tree has no conflicts.
#     Example: `git merge --no-ff feature` after both sides advanced.
#
# SCOPE — what this hook does NOT cover (and what does):
#   - Conflict-resolution commits: when `git merge` produces conflicts, the
#     user edits files and runs `git commit`. That fires pre-commit normally,
#     not pre-merge-commit. So pre-commit remains the authority for conflict-
#     resolved content.
#   - Fast-forward merges: `git merge` that only advances HEAD fires NO
#     hooks at all (no merge commit is created). The only guard is CI.
#   - `git merge --squash`: creates an index state but requires a manual
#     `git commit`. That fires pre-commit, not pre-merge-commit.
#   - `git cherry-pick`, `git rebase`, `git rebase --continue`: bypass
#     BOTH pre-commit AND pre-merge-commit. Only CI catches issues
#     introduced by these paths.
#
# In every bypassed path above, CI is the final backstop. Specifically:
#   - .github/workflows/lint-error-codes.yml enforces the cspell
#     lint-error-code contract on every PR touching hook/lint surface.
#   - scripts/validate-lint-error-codes.ps1 is the underlying validator
#     that the CI workflow runs; it roundtrips every [A-Z]{2,}\d{3} prefix
#     emitted by any lint/test/hook file through cspell.
#
# HISTORICAL CONTEXT:
#   On 2026-04-19 a new skill file introduced 5 occurrences of the token
#   `PWS` (part of lint-error-code names like `PWS001`). cspell had no
#   entry for `PWS`. The change landed via a merge commit, so pre-commit
#   did not run. The failure surfaced at pre-push and blocked the whole
#   batch. This hook plus the CI workflow together close that gap.
#
# WHAT THIS HOOK DOES:
#   Delegates (exec) to the pre-commit hook. pre-commit already derives the
#   staged-file set from `git diff --cached --name-only --diff-filter=ACM`,
#   which correctly reflects the pending merge commit's changed content.
#
# BYPASS:
#   `git merge --no-verify` skips this hook, same as pre-commit. CI is the
#   final backstop.
# ============================================================================

set -e

SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
PRE_COMMIT="$SCRIPT_DIR/pre-commit"

if [[ ! -x "$PRE_COMMIT" ]]; then
  echo "Error: pre-commit hook not found or not executable at $PRE_COMMIT" >&2
  echo "Run 'npm run hooks:install' to restore hook permissions." >&2
  exit 1
fi

exec "$PRE_COMMIT" "$@"