I have been reviewing this pull request. I believe that we will need both the .archive_path tag as well as the .path tag as well as both the .archive_format take as well as the .format tag, since it is common practice to archive sets of data sets, with, say a bzipped tar, and still have each dataset be a multi-image container, e.g. hdf5 or even imgcif, which is
well able to carry multiple images in a single file. Ideally we should allow this to arbitrary
depth, but certainly at least to depth 2, so we can at least point to a tarball of hdf5 files

Yes, this is the intention of this pull request. The _array_data_external_data.{path,format} tags are already present in 1.8.5, just the archive_{format,path} ones were missing.

Took care of this in new cif_img_1.8.6 just added to main