SUMMARY.md / Table of Contents: Parts are being ignored

[NeatNit]

SUMMARY.md currently looks like this:

# The Rust Programming Language

(Intro stuff)

## Getting started

- (Chapters 1 to 6)

## Basic Rust Literacy

- (Chapters 7 to 12)

## Thinking in Rust

- (Chapters 13 to 18)

## Advanced Topics

- (Chapters 19 to 21 + Appendix)

None of the headers are actually being used. This is because:

1. The first header # The Rust Programming Language is always ignored.
2. All headers after that must be h1, otherwise they are ignored too.

This is according to:
https://rust-lang.github.io/mdBook/format/summary.html

1. Title - While optional, it’s common practice to begin with a title, generally # Summary. This is ignored by the parser however, and can be omitted.

[..]

3. Part Title - Level 1 headers can be used as a title for the following numbered chapters. [..]. Part titles must be h1 headers (one #), other heading levels are ignored.

This seems like a mistake, assuming the part titles were meant to be visible. The fix is easy:

-## Getting started
+# Getting started

-## Basic Rust Literacy
+# Basic Rust Literacy

etc.

[carols10cents]

What do you mean by ignored? That is, what is the effect you're observing? When I do mdbook build on the current main branch, I see the table of contents as I expect in the sidebar?

[carols10cents]

OH you only mean those 4 H2s -- yeah those are outdated. That was how we thought of the book at one time and then it became more chapter based as we got closer to print. I'm just going to remove those because they're indeed unused-- please clarify if I'm still misunderstanding.

[NeatNit]

Yup, that's exactly what I meant. If they're not intended to be part of the book's structure anymore, removing them is probably best.