webdav: fix SetModTime erasing checksums on owncloud and nextcloud

Before this change, calling SetModTime on owncloud and nextcloud would
inadvertently erase the object's stored hashes. This change fixes the issue,
which was discovered by the bisync integration tests.

backend/webdav/webdav.go

@@ -759,7 +759,7 @@ func (f *Fs) listAll(ctx context.Context, dir string, directoriesOnly bool, file
 		}
 		return found, fmt.Errorf("couldn't list files: %w", err)
 	}
-	//fmt.Printf("result = %#v", &result)
+	// fmt.Printf("result = %#v", &result)
 	baseURL, err := rest.URLJoin(f.endpoint, opts.Path)
 	if err != nil {
 		return false, fmt.Errorf("couldn't join URL: %w", err)
@@ -1110,7 +1110,7 @@ func (f *Fs) copyOrMove(ctx context.Context, src fs.Object, remote string, metho
 	if err != nil {
 		return nil, fmt.Errorf("copy NewObject failed: %w", err)
 	}
-	if f.useOCMtime && resp.Header.Get("X-OC-Mtime") != "accepted" && f.propsetMtime {
+	if f.useOCMtime && resp.Header.Get("X-OC-Mtime") != "accepted" && f.propsetMtime && !dstObj.ModTime(ctx).Equal(src.ModTime(ctx)) {
 		fs.Debugf(dstObj, "Setting modtime after copy to %v", src.ModTime(ctx))
 		err = dstObj.SetModTime(ctx, src.ModTime(ctx))
 		if err != nil {
@@ -1364,15 +1364,38 @@ var owncloudPropset = `<?xml version="1.0" encoding="utf-8" ?>
 </D:propertyupdate>
 `
 
+var owncloudPropsetWithChecksum = `<?xml version="1.0" encoding="utf-8" ?>
+<D:propertyupdate xmlns:D="DAV:" xmlns:oc="http://owncloud.org/ns">
+ <D:set>
+  <D:prop>
+   <lastmodified xmlns="DAV:">%d</lastmodified>
+   <oc:checksums>
+	<oc:checksum>%s</oc:checksum>
+   </oc:checksums>
+  </D:prop>
+ </D:set>
+</D:propertyupdate>
+`
+
 // SetModTime sets the modification time of the local fs object
 func (o *Object) SetModTime(ctx context.Context, modTime time.Time) error {
 	if o.fs.propsetMtime {
+		checksums := ""
+		if o.fs.hasOCSHA1 && o.sha1 != "" {
+			checksums = "SHA1:" + o.sha1
+		} else if o.fs.hasOCMD5 && o.md5 != "" {
+			checksums = "MD5:" + o.md5
+		}
+
 		opts := rest.Opts{
 			Method:     "PROPPATCH",
 			Path:       o.filePath(),
 			NoRedirect: true,
 			Body:       strings.NewReader(fmt.Sprintf(owncloudPropset, modTime.Unix())),
 		}
+		if checksums != "" {
+			opts.Body = strings.NewReader(fmt.Sprintf(owncloudPropsetWithChecksum, modTime.Unix(), checksums))
+		}
 		var result api.Multistatus
 		var resp *http.Response
 		var err error
@@ -1395,6 +1418,14 @@ func (o *Object) SetModTime(ctx context.Context, modTime time.Time) error {
 			o.modTime = modTime
 			return nil
 		}
+		// got an error, but it's possible it actually worked, so double-check
+		newO, err := o.fs.NewObject(ctx, o.remote)
+		if err != nil {
+			return err
+		}
+		if newO.ModTime(ctx).Equal(modTime) {
+			return nil
+		}
 		// fallback
 		return fs.ErrorCantSetModTime
 	}
@@ -1521,7 +1552,6 @@ func (o *Object) updateSimple(ctx context.Context, body io.Reader, getBody func(
 		return err
 	}
 	return nil
-
 }
 
 // Remove an object

cmd/bisync/bisync_test.go

@@ -90,6 +90,7 @@ var logReplacements = []string{
 	`^NOTICE: .*?: Forced to upload files to set modification times on this backend.$`, dropMe,
 	`^INFO  : .*? Committing uploads - please wait...$`, dropMe,
 	`^INFO  : .*?: src and dst identical but can't set mod time without deleting and re-uploading$`, dropMe,
+	`^INFO  : .*?: src and dst identical but can't set mod time without re-uploading$`, dropMe,
 	// ignore crypt info messages
 	`^INFO  : .*?: Crypt detected! Using cryptcheck instead of check. \(Use --size-only or --ignore-checksum to disable\)$`, dropMe,
 	// ignore drive info messages