[Deviantart] `extra` flag causes posts to be expanded before they are excluded by archive

[awiebe]

If I have correctly understood the extractor code it looks like there are a number of flags that can be passed to the deviantart extractor which causes it to always expand posts because the extractor needs this call to get the post data.

However, depending on whether I am trying to sync older posts rescanning for post metadata, or just get extras for new posts; this may be undesirable behaviour.

In many circumstances I want the posts to be excluded by the archive file before going to the trouble of expanding it.

I don't know if gallery-dl architecture supports this, but the two reasonable solutions I can think of are:

1. In the extractor before expanding the post, check the archive file for the post slug. Do not expand the post if the slug is present.
2. If the gallery-dl architecture supports it, then do not expand the post before pushing back up the urls. Only expand the posts if there is a hook for after filtering.

And then additionally you might want always_expand_metadata which does not try to be smart about it in case you also want to rescan all of the prior posts. (i.e. do current behaviour)

[mikf]

This has been an unresolved issue since forever: #317