Hard-tab support

[Xophmeister]

At the risk of starting a Holy War, (#indent-level! 4) implies soft-tabs; i.e., a number of spaces. Some people prefer hard-tabs (i.e., a single \t at each indentation level) and some codebases -- misguided though they may be -- expect them per their style guide.

I propose updating the format of this directive such that its parameter is either:

• A digit, representing the number of spaces in a soft-tab (as now);
• Or a t, say, representing hard-tab indentation.

[aspiwack]

Why not.

It isn't something that is needed for the first release. But when that's done, it will be something to consider.

[figsoda]

What if we rename it to #indent! and accept arbitrary strings, the word level doesn't make as much sense to me with tabs

we can also rely on the general_predicates instead of regex for parsing queries

a little off-topic but maybe there can also be a placeholder language only for query parsing, and we can have a format for some sort of "header node" like this:

((#language! rust) (#indent! "\t"))
; ...

[haikyuu]

More than a preference, some languages actually require using tabs. i.e imba.
I'm actually working on its tree-sitter grammar and I want to use topiary at some point to format imba code.