Pull request overview

Tightens .idx/.rev parsing and LazyIndex initialization validation to reject unsupported versions and detect corrupted fanout / reverse-index data, with expanded tests and fuzz coverage.

Changes:

• Enforce strict idx version matching and validate fanout monotonicity during decode/init.
• Rework LazyIndex.EntriesByOffset() to stream offset order via .rev rather than allocating + sorting, and update tests accordingly.
• Improve error handling in packfile parsing callbacks and expand error-path tests/fuzzing for idx/rev decoding.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

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Pull request overview

Copilot reviewed 7 out of 8 changed files in this pull request and generated no new comments.

func readOffsets(idx *MemoryIndex, r io.Reader) error {
	var o64cnt int64
	for k := range fanout {
		if pos := idx.FanoutMapping[k]; pos != noMapping {
			if _, err := io.ReadFull(r, idx.Offset32[pos]); err != nil {
				return err
			}

			for p := 0; p < len(idx.Offset32[pos]); p += 4 {
				if idx.Offset32[pos][p]&(byte(1)<<7) > 0 {
					o64cnt++
				}
			}
		}
	}

	if o64cnt > 0 {
		idx.Offset64 = make([]byte, o64cnt*8)
		if _, err := io.ReadFull(r, idx.Offset64); err != nil {

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