#!/usr/bin/env bash
# Keep docs/traceability.md in step with the tags in the tree.
#
# The gate regenerates the matrix in CI and fails if the result differs from
# what is committed. That is the right check — a matrix that disagrees with the
# tree is worse than none, because it is read as current — but it fails *after*
# a push, on a commit that is otherwise fine, and it has now done so on six
# commits in a row because adding a `TRACES:` tag and regenerating the matrix
# are two actions and only the first is on anyone's mind.
#
# So it happens here instead, where the tags are being changed.
#
# Only when something that can carry a tag is staged: a commit touching
# workflows, packaging or the matrix itself pays nothing.
set -euo pipefail

staged="$(git diff --cached --name-only --diff-filter=ACMR)"
if ! grep -qE '\.(rs|slint|yaml|md)$' <<< "${staged}"; then
    exit 0
fi
# The matrix is generated from the tree, so regenerating it because it was
# itself edited would be circular.
if [ "$(tr -d '[:space:]' <<< "${staged}")" = "docs/traceability.md" ]; then
    exit 0
fi

repo="$(git rev-parse --show-toplevel)"
cd "${repo}"

# Quiet unless it has something to say. A hook that prints on every commit is
# a hook people start passing --no-verify to.
if ! cargo run -q -p traceability -- report >/dev/null 2>&1; then
    echo "pre-commit: could not run the traceability report; leaving the matrix alone" >&2
    exit 0
fi

if ! git diff --quiet -- docs/traceability.md; then
    git add docs/traceability.md
    echo "pre-commit: regenerated docs/traceability.md and staged it"
fi