It's possible to loose the history of an attachment when the document metadata dirty flag is false

When the document dirty flag is false, the filesystem attachment store assume the attachment contains the archive. Problem is that the archive is supposed to be lazy loaded, so AttachmentSaveTransactionRunnable should use the right getAttachmentArchive(XWikiContext) API instead of getAttachment_archive() to know if the attachment has an archive.

The workaround is to load the attachment archive before saving the document.