gs/swift: calculate md5 content hash for upload

internal/backend/gs/gs.go

@@ -3,6 +3,7 @@ package gs
 
 import (
 	"context"
+	"crypto/md5"
 	"hash"
 	"io"
 	"net/http"
@@ -191,7 +192,7 @@ func (be *Backend) Location() string {
 
 // Hasher may return a hash function for calculating a content hash for the backend
 func (be *Backend) Hasher() hash.Hash {
-	return nil
+	return md5.New()
 }
 
 // Path returns the path in the bucket that is used for this backend.
@@ -240,6 +241,7 @@ func (be *Backend) Save(ctx context.Context, h restic.Handle, rd restic.RewindRe
 	// uploads are not providing significant benefit anyways.
 	w := be.bucket.Object(objName).NewWriter(ctx)
 	w.ChunkSize = 0
+	w.MD5 = rd.Hash()
 	wbytes, err := io.Copy(w, rd)
 	cerr := w.Close()
 	if err == nil {

internal/backend/swift/swift.go

@@ -2,6 +2,8 @@ package swift
 
 import (
 	"context"
+	"crypto/md5"
+	"encoding/hex"
 	"fmt"
 	"hash"
 	"io"
@@ -118,7 +120,7 @@ func (be *beSwift) Location() string {
 
 // Hasher may return a hash function for calculating a content hash for the backend
 func (be *beSwift) Hasher() hash.Hash {
-	return nil
+	return md5.New()
 }
 
 // Load runs fn with a reader that yields the contents of the file at h at the
@@ -184,7 +186,7 @@ func (be *beSwift) Save(ctx context.Context, h restic.Handle, rd restic.RewindRe
 
 	debug.Log("PutObject(%v, %v, %v)", be.container, objName, encoding)
 	hdr := swift.Headers{"Content-Length": strconv.FormatInt(rd.Length(), 10)}
-	_, err := be.conn.ObjectPut(be.container, objName, rd, true, "", encoding, hdr)
+	_, err := be.conn.ObjectPut(be.container, objName, rd, true, hex.EncodeToString(rd.Hash()), encoding, hdr)
 	// swift does not return the upload length
 	debug.Log("%v, err %#v", objName, err)