lfs: implement CatFileBatchScanner.ContentsSha()

lfs/gitscanner_catfilebatch.go

@@ -3,6 +3,7 @@ package lfs
 import (
 	"bufio"
 	"bytes"
+	"crypto/sha256"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -64,9 +65,10 @@ type CatFileBatchScanner struct {
 	w       io.Writer
 	closeFn func() error
 
-	blobSha string
-	pointer *WrappedPointer
-	err     error
+	blobSha     string
+	contentsSha string
+	pointer     *WrappedPointer
+	err         error
 }
 
 func NewCatFileBatchScanner() (*CatFileBatchScanner, error) {
@@ -99,6 +101,10 @@ func (s *CatFileBatchScanner) BlobSHA() string {
 	return s.blobSha
 }
 
+func (s *CatFileBatchScanner) ContentsSha() string {
+	return s.contentsSha
+}
+
 func (s *CatFileBatchScanner) Pointer() *WrappedPointer {
 	return s.pointer
 }
@@ -109,6 +115,7 @@ func (s *CatFileBatchScanner) Err() error {
 
 func (s *CatFileBatchScanner) Scan(sha []byte) bool {
 	s.pointer, s.err = nil, nil
+	s.blobSha, s.contentsSha = "", ""
 
 	if s.w != nil && sha != nil {
 		if _, err := fmt.Fprintf(s.w, "%s\n", sha); err != nil {
@@ -117,8 +124,9 @@ func (s *CatFileBatchScanner) Scan(sha []byte) bool {
 		}
 	}
 
-	b, p, err := s.next()
+	b, c, p, err := s.next()
 	s.blobSha = b
+	s.contentsSha = c
 	s.pointer = p
 
 	if err != nil {
@@ -138,41 +146,46 @@ func (s *CatFileBatchScanner) Close() error {
 	return s.closeFn()
 }
 
-func (s *CatFileBatchScanner) next() (string, *WrappedPointer, error) {
+func (s *CatFileBatchScanner) next() (string, string, *WrappedPointer, error) {
 	l, err := s.r.ReadBytes('\n')
 	if err != nil {
-		return "", nil, err
+		return "", "", nil, err
 	}
 
 	// Line is formatted:
 	// <sha1> <type> <size>
 	fields := bytes.Fields(l)
 	if len(fields) < 3 {
-		return "", nil, errors.Wrap(fmt.Errorf("Invalid: %q", string(l)), "git cat-file --batch")
+		return "", "", nil, errors.Wrap(fmt.Errorf("Invalid: %q", string(l)), "git cat-file --batch")
 	}
 
 	blobSha := string(fields[0])
 	size, _ := strconv.Atoi(string(fields[2]))
+	sha := sha256.New()
 	buf := make([]byte, size)
-	read, err := io.ReadFull(s.r, buf)
+	read, err := io.ReadFull(io.TeeReader(s.r, sha), buf)
 	if err != nil {
-		return blobSha, nil, err
+		return blobSha, "", nil, err
 	}
 
 	if size != read {
-		return blobSha, nil, fmt.Errorf("expected %d bytes, read %d bytes", size, read)
+		return blobSha, "", nil, fmt.Errorf("expected %d bytes, read %d bytes", size, read)
 	}
 
 	p, err := DecodePointer(bytes.NewBuffer(buf[:read]))
 	var pointer *WrappedPointer
+	var contentsSha string
 	if err == nil {
+		contentsSha = p.Oid
 		pointer = &WrappedPointer{
 			Sha1:    blobSha,
 			Pointer: p,
 		}
+	} else {
+		contentsSha = fmt.Sprintf("%x", sha.Sum(nil))
 	}
 
 	_, err = s.r.ReadBytes('\n') // Extra \n inserted by cat-file
 
-	return blobSha, pointer, err
+	return blobSha, contentsSha, pointer, err
 }