Support TODO dependencies

[NickHu]

Does this feature exist in Emacs orgmode core?

Yes

Orgmode link

https://orgmode.org/manual/TODO-dependencies.html

Feature value

No response

Additional context

I have a lot of tasks without deadlines/scheduled times, but they naturally form a kind of dependency hierarchy. Because they don't have an attached time, they don't show up in the agenda view, but only in the List of all TODO entries (<leader>oat); however, this is quite an overwhelming view when dependencies are not accounted for. The documentation says that in the Emacs version, blocked tasks can be dimmed/filtered out.

[jgollenz]

I think that's a useful feature. If you haven't started on this @kristijanhusak, I'd like to give it a go

[NickHu]

I had a bit of a think about this and I think the best approach would be to support 'Special Properties' first: https://orgmode.org/manual/Special-Properties.html#Special-Properties, and then utilise the BLOCKED property to implement this

[kristijanhusak]

@jgollenz I didn't start on it, you can go ahead.
@NickHu some of these are implemented, but not all.

[jgollenz]

@kristijanhusak regarding the special properties: is that something that every headline just has or do they have to be set explicitly? E.g. FILE is something that all headlines just have, even if we don't set it, correct?