Pre-commit hook fails when pyproject.toml is staged without dependency-line changes

[gkennos]

The canonical pre-commit hook can exit with status 1 when pyproject.toml is staged but the staged diff does not contain any quoted dependency lines.

This is separate from #3

That issue covers the macOS/BSD sed portability problem where \s leaves the diff marker in the extracted package name. This issue covers the empty-match path under set -euo pipefail

The hook currently builds dependency candidates with a pipeline like:

changed_names=$(git diff --cached -- pyproject.toml \
    | grep -E '^[+-]\s*"[A-Za-z0-9][A-Za-z0-9._-]*' \
    | sed -E 's/^[+-]\s*"([A-Za-z0-9][A-Za-z0-9._-]*).*/\1/' \
    | sort -u)

If pyproject.toml is staged but no dependency-like line matches, grep exits 1

Because the hook uses set -euo pipefail, the command substitution exits before the later empty-result guard can run

proposed fix:

changed_names=$(git diff --cached -- pyproject.toml \
    | sed -nE 's/^[+-][[:space:]]*"([A-Za-z0-9][A-Za-z0-9._-]*).*/\1/p' \
    | sort -u)

this will also fix #3