[e621] extract extended metadata using e621-specific API endpoints

[ClosedPort22]

This is more of a discussion on the best way to implement features that are specific to e621. Considering that e621 "is a heavily modified fork of Danbooru", it may be necessary to separate e621 from the Danbooru extractors sooner or later.

Summary of the changes in this PR:

• Extract notes using the /notes.json API endpoint
• Extract pool metadata even when the subcategory is not "pool"
• Treat e926 as a separate instance of e621. This allows the user to use different options for e621 and e926. However, the old config will no longer apply to e926.

While working on e621 I found that the Favorites extractor did not work for aibooru, so I've disabled it in supportedsites.py and left a TODO comment.

[mikf]

So you want to undo the "merge danbooru and e621 code" part from 563bd0e? I guess it is better that way, given the increasingly large differences.

I wouldn't inherit from DanbooruExtractor, though. Just do a clean split between the two sites and remove everything e621 specific from danbooru, like the FavoriteExtractor or this code here

gallery-dl/gallery_dl/extractor/danbooru.py

Lines 70 to 80 in 4611237

	file = post.get("file")
	if file:
	url = file["url"]
	if not url:
	md5 = file["md5"]
	url = file["url"] = (
	"https://static1.{}/data/{}/{}/{}.{}".format(
	self.root[8:], md5[0:2], md5[2:4], md5, file["ext"]
	))
	post["filename"] = file["md5"]
	post["extension"] = file["ext"]

---

If you want, I can also do this myself (in maybe a cleaner way) and you redo your metadata related changes after.

I would generally prefer not to include too many changes into one PR if possible. Also, git commit --amend makes it possible to "combine" commits and not have a new commit for every single change.

[ClosedPort22]

I wouldn't inherit from DanbooruExtractor, though. Just do a clean split between the two sites and remove everything e621 specific from danbooru, like the FavoriteExtractor or this code here

Wouldn't that re-introduce some of the duplicate code, though? I wanted to be sure other Danbooru instances didn't break, since I didn't use them as often. I guess I missed some of the obvious e621-specific code...

If you want, I can also do this myself (in maybe a cleaner way) and you redo your metadata related changes after.

That would be fine, since this is mostly just a discussion. Thanks in advance.

I would generally prefer not to include too many changes into one PR if possible. Also, git commit --amend makes it possible to "combine" commits and not have a new commit for every single change.

I rewrite Git history a lot (including using git commit --amend) actually. I generally try to keep my commits small and follow the "atomic" commit principle. My apologies for the large pull requests (#3469 is even bigger than this). I'll make them smaller in the future.