Function scanTree

plumbing/object/commit_scanner.go:75–98

scanTree expects the first non-empty header to be `tree HASH`. Anything else (or an empty buffer) is rejected with ErrMalformedCommit, matching upstream's `bogus commit object` check.

(s *commitScanner)

// else (or an empty buffer) is rejected with ErrMalformedCommit, matching
// upstream's `bogus commit object` check.
func scanTree(s *commitScanner) (commitState, error) {
	line, err := s.readLine()
	if err != nil && err != io.EOF {
		return nil, err
	}
	if len(line) == 0 || isBlankLine(line) {
		return nil, fmt.Errorf("%w: missing tree header", ErrMalformedCommit)
	}

	key, data := splitHeader(line)
	if key != "tree" {
		return nil, fmt.Errorf("%w: tree header must be first", ErrMalformedCommit)
	}
	h, herr := parseObjectIDHex(data, ErrMalformedCommit, "tree")
	if herr != nil {
		return nil, herr
	}
	s.c.TreeHash = h
	s.sawTree = true
	if err == io.EOF {
		return nil, nil
	}
	return scanParents, nil
}

// scanParents consumes contiguous `parent HASH` lines. The first non-parent
// line ends the parent block and is handed off to scanAuthor; any later