editor: move RevisionData on the filesystem over a given threshold The implementation is similar to the one in mercurial.patch except the mode and copy information are currently kept outside. It minimizes changes to RevisionData and helps with files which properties are modified but not their contents, which filestore was not designed to handle. Besides, CopiedFile pushed from the editor may later be handled separately to resolve them at commit time, in which case we would store the metadata outside of the file stores.