filen: fix incorrect in-memory modtime after upload

Put and Update were returning Objects whose in-memory modtime was the
nanosecond-precision source modtime, while the server stores
millisecond precision. After the upload returned, the in-memory state
did not match what a fresh List would report, which broke wrappers
that compare modtimes (e.g. the hasher backend's fingerprint).

The standard for backends is to re-read metadata after Upload so this
re-reads the file via FindFile after the upload completes so the
Object reflects the server's authoritative state. The chunked upload
path already re-reads via NewObject in multiThreadCopy, so this only
needs to apply to Put and Update.

Fixes #9308

backend/filen/filen.go

@@ -339,7 +339,10 @@ func (f *Fs) Put(ctx context.Context, in io.Reader, src fs.ObjectInfo, options .
 	if err != nil {
 		return nil, err
 	}
-	uploadedFile, err := f.filen.UploadFile(ctx, incompleteFile, in)
+	if _, err := f.filen.UploadFile(ctx, incompleteFile, in); err != nil {
+		return nil, err
+	}
+	uploadedFile, err := f.readMetadata(ctx, resolvedPath)
 	if err != nil {
 		return nil, err
 	}
@@ -350,6 +353,22 @@ func (f *Fs) Put(ctx context.Context, in io.Reader, src fs.ObjectInfo, options .
 	}, nil
 }
 
+// readMetadata re-reads the file's metadata from the server after an
+// upload so the in-memory state reflects what is actually stored
+// (e.g. modtime at the server's precision). Without this, callers
+// would see higher-precision modtimes locally than List would return,
+// breaking layers like the hasher backend that fingerprint by modtime.
+func (f *Fs) readMetadata(ctx context.Context, resolvedPath string) (*types.File, error) {
+	file, err := f.filen.FindFile(ctx, resolvedPath)
+	if err != nil {
+		return nil, err
+	}
+	if file == nil {
+		return nil, fs.ErrorObjectNotFound
+	}
+	return file, nil
+}
+
 // PutStream uploads to the remote path with the modTime given of indeterminate size
 //
 // May create the object even if it returns an error - if so
@@ -760,7 +779,10 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	newIncomplete.LastModified = newModTime
 	newIncomplete.Created = newModTime
 	newIncomplete.SetMimeType(fs.MimeType(ctx, src))
-	uploadedFile, err := o.fs.filen.UploadFile(ctx, newIncomplete, in)
+	if _, err := o.fs.filen.UploadFile(ctx, newIncomplete, in); err != nil {
+		return err
+	}
+	uploadedFile, err := o.fs.readMetadata(ctx, o.fs.resolvePath(o.path))
 	if err != nil {
 		return err
 	}