Allow unindent without selection

[KoBeWi]

Revival of #50289
Fixes #50279
Fixes #68154

[KoBeWi]

This seems to fail 2 test cases.

test[tab]

is expected to become

test

after unindent (i.e. whitespace to the right is removed). This behavior is probably what caused the original issue. Any reason why it would work like that? Is it common in code editors?

[KoBeWi]

Rebased. I also changed the failing test. tbh the two behaviors aren't really conflicting (i.e. Shift+Tab can remove trailing tab and unindent if there isn't one), but I'm just reviving a PR here; it's not like I know what it does >_>

@Paulb23 Review would be appreciated, the issue gets in my way too often.

[MewPurPur]

Makes sense to me. I don't see why the current implementation would be desired - if I need to remove whitespace, I can just press Backspace. Idk about removing previous whitespace, instead of just tabs at the beginning of a line, but it seems pointless to me.

[KoBeWi]

I reworked the PR. It no longer removes do_unindent(), it simply changes the method used for dedent action.

[Paulb23]

I would continue to remove do_unindent then I think we can merge this for 4.0, as this would fix #68154. Otherwise it requires a bit of a rework for multi-carets. Can add it back later if needed.

[akien-mga]

What's the difference between the remaining do_indent and indent_lines?

[Paulb23]

Some of those test are probably still worth keeping.

What's the difference between the remaining do_indent and indent_lines?

do_indent is called when the user presses tab, so will insert a tab/space at the caret(s). However, if there is a selection it will call indent_lines, which will move / indent lines that have a caret or selection. Similar to how the JetBrains IDE's work.

[KoBeWi]

Some of those test are probably still worth keeping.

So should I change them to unindent_lines()? Which ones exactly?

[Paulb23]

So should I change them to unindent_lines()? Which ones exactly?

Yeah I think most of them should be okay apart from the ones under the /* Should indent inplace. */ heading.

[akien-mga]

Thanks!