JanDeDobbeleer/oh-my-posh · error

gitstatus: delta target size mismatch

Error message

gitstatus: delta target size mismatch

What it means

After applying all delta opcodes, applyDelta compares the reconstructed buffer length with the target size decoded from the delta header. A mismatch means the opcode stream did not reproduce exactly targetSize bytes - the delta is corrupt, incomplete, or was misparsed.

Source

Thrown at src/gitstatus/objectstore.go:463

			}
			result = append(result, base[offset:offset+size]...)
			continue
		}

		if op == 0 {
			return nil, errors.New("gitstatus: invalid delta opcode")
		}

		// insert literal of length op
		if int(op) > len(delta) {
			return nil, errors.New("gitstatus: truncated delta insert")
		}
		result = append(result, delta[:op]...)
		delta = delta[op:]
	}

	if int64(len(result)) != targetSize {
		return nil, errors.New("gitstatus: delta target size mismatch")
	}

	return result, nil
}

// decodeSizeVarint reads git's little-endian size varint (used in delta
// headers), distinct from the big-endian offset varint.
func decodeSizeVarint(data []byte) (v int64, n int) {
	shift := uint(0)
	for {
		if n >= len(data) {
			return 0, 0
		}
		b := data[n]
		n++
		v |= int64(b&0x7f) << shift
		if b&0x80 == 0 {
			return v, n

View on GitHub (pinned to 0976794618)

Solutions

1. Re-download/re-clone to replace the corrupted packfile
2. Re-check opcode decode loop: ensure copy opcodes consume size+offset varints and inserts advance delta by exactly op bytes
3. Assert targetSize > 0 and base size matches the delta's declared base before applying
4. Validate pack checksum (SHA-1 trailer) before delta application to fail early with a clearer error

Example fix

// before
result, err := applyDelta(base, delta, targetSize)
// after
if int64(len(base)) == 0 && targetSize > 0 { return nil, errors.New("empty base for delta") }
result, err := applyDelta(base, delta, targetSize)

if int64(len(base)) == 0 && targetSize > 0 {
    return nil, errors.New("empty base for non-empty delta target")
}

func deltaApplicable(baseLen, targetSize int64) bool {
    return targetSize == 0 || baseLen > 0
}

When it happens

Trigger: applyPackDelta feeds applyDelta a delta whose opcodes produce fewer or more bytes than the header's target size, typically because the delta stream is truncated/corrupt or opcode length fields were decoded incorrectly (e.g. copy-size varint misread).

Common situations: Corrupted packfiles after a failed network transfer; writing a custom pack reader with wrong varint endianness for copy offset/size fields; partial reads when streaming packs from disk or network.

Related errors

• gitstatus: truncated delta insert
• font %v has no name table
• gitstatus: reftables HEAD requires exec fallback
• gitstatus: staged adds and deletes may be renames, deferring
• unclosed section:

AI-assisted analysis of JanDeDobbeleer/oh-my-posh@0976794618 (2026-08-31). Data as JSON: /api/errors/8f75b3eecaafd05b. Report an issue: GitHub.