Refactor parseObj to use io.Reader interface instead of ioutil

@DanielleSucher FTW!

object.go

@@ -15,6 +15,43 @@ import (
	"time"
)

type scanner struct {
	r    io.Reader
	data []byte
	err  error
}

func (s *scanner) scan() bool {
	if s.err != nil {
		return false
	}
	s.data = s.read()
	return s.err == nil
}

func (s *scanner) Err() error {
	if s.err == io.EOF {
		return nil
	}
	return s.err
}

func (s *scanner) read() []byte {
	if s.err != nil {
		return nil
	}
	result := make([]byte, 1)
	n, err := s.r.Read(result)
	if err != nil {
		s.err = err
		return nil
	}
	if n == 0 {
		s.err = fmt.Errorf("read zero bytes")
	}
	return result
}

const (
	RFC2822 = "Mon Jan 2 15:04:05 2006 -0700"
)
@@ -206,27 +243,37 @@ func normalizePerms(perms string) string {
}

func parseObj(r io.Reader, name SHA, basedir string) (result GitObject, err error) {
	// TODO fixme
	bts, err := ioutil.ReadAll(r)
	if err != nil {
		return result, err

	var resultType string
	var resultSize string
	scnr := scanner{r, nil, nil}
	for scnr.scan() {
		txt := string(scnr.data)
		if txt == " " {
			break
		}
		resultType += txt
	}
	obj := bts

	parts := bytes.Split(obj, []byte("\x00"))
	parts = bytes.Fields(parts[0])
	resultType := string(parts[0])
	resultSize := string(parts[1])
	nullIndex := bytes.Index(obj, []byte("\x00"))
	for scnr.scan() {
		txt := string(scnr.data)
		if txt == "\x00" {
			break
		}
		resultSize += txt
	}

	if scnr.Err() != nil {
		return nil, scnr.Err()
	}

	switch resultType {
	case "commit":
		return parseCommit(bytes.NewReader(obj[nullIndex+1:]), resultSize, name)
		return parseCommit(r, resultSize, name)
	case "tree":
		return parseTree(bytes.NewReader(obj), resultSize, basedir)

		return parseTree(r, resultSize, basedir)
	case "blob":
		return parseBlob(bytes.NewReader(obj[nullIndex+1:]), resultSize)
		return parseBlob(r, resultSize)
	default:
		err = fmt.Errorf("Received unknown object type %s", resultType)
	}
@@ -317,11 +364,6 @@ func parseTree(r io.Reader, resultSize string, basedir string) (Tree, error) {

		if count == 0 {
			// the first time through, scanner.Text() will be
			// "tree <size>"
			continue
		}
		if count == 1 {
			// the second time through, scanner.Text() will be
			// <perms> <filename>
			// separated by a space
			fields := strings.Fields(txt)
@@ -330,7 +372,7 @@ func parseTree(r io.Reader, resultSize string, basedir string) (Tree, error) {
			continue
		}

		// after the second time through, scanner.Text() will be
		// after the first time through, scanner.Text() will be
		// <sha><perms2> <file2>
		// where perms2 and file2 refer to the permissions and filename (respectively)
		// of the NEXT object, and <sha> is the first 20 bytes exactly.