Use consistent sentence case for section headers

There was a mix of different capitalization here, so I'm just going to
pick the one we use most often.

CONTRIBUTING.md

@@ -56,11 +56,11 @@ mdBook builds on stable Rust, if you want to build mdBook from source, here are
 
 The resulting binary can be found in `mdBook/target/debug/` under the name `mdbook` or `mdbook.exe`.
 
-## Code Quality
+## Code quality
 
 We love code quality and Rust has some excellent tools to assist you with contributions.
 
-### Formatting Code with rustfmt
+### Formatting code with rustfmt
 
 Before you make your Pull Request to the project, please run it through the `rustfmt` utility.
 This will ensure we have good quality source code that is better for us all to maintain.
@@ -84,7 +84,7 @@ The quick guide is
 
 For more information, such as running it from your favourite editor, please see the `rustfmt` project. [rustfmt](https://github.com/rust-lang/rustfmt)
 
-### Finding Issues with Clippy
+### Finding issues with clippy
 
 [Clippy](https://doc.rust-lang.org/clippy/) is a code analyser/linter detecting mistakes, and therefore helps to improve your code.
 Like formatting your code with `rustfmt`, running clippy regularly and before your Pull Request will help us maintain awesome code.

guide/src/SUMMARY.md

@@ -2,15 +2,15 @@
 
 [Introduction](README.md)
 
-# User Guide
+# User guide
 
 - [Installation](guide/installation.md)
-- [Reading Books](guide/reading.md)
-- [Creating a Book](guide/creating.md)
+- [Reading books](guide/reading.md)
+- [Creating a book](guide/creating.md)
 
-# Reference Guide
+# Reference guide
 
-- [Command Line Tool](cli/README.md)
+- [Command-line tool](cli/README.md)
     - [init](cli/init.md)
     - [build](cli/build.md)
     - [watch](cli/watch.md)
@@ -25,18 +25,18 @@
         - [General](format/configuration/general.md)
         - [Preprocessors](format/configuration/preprocessors.md)
         - [Renderers](format/configuration/renderers.md)
-        - [Environment Variables](format/configuration/environment-variables.md)
+        - [Environment variables](format/configuration/environment-variables.md)
     - [Theme](format/theme/README.md)
         - [index.hbs](format/theme/index-hbs.md)
         - [Syntax highlighting](format/theme/syntax-highlighting.md)
         - [Editor](format/theme/editor.md)
-    - [MathJax Support](format/mathjax.md)
+    - [MathJax support](format/mathjax.md)
     - [mdBook-specific features](format/mdbook.md)
     - [Markdown](format/markdown.md)
-- [Continuous Integration](continuous-integration.md)
-- [For Developers](for_developers/README.md)
+- [Continuous integration](continuous-integration.md)
+- [For developers](for_developers/README.md)
     - [Preprocessors](for_developers/preprocessors.md)
-    - [Alternative Backends](for_developers/backends.md)
+    - [Alternative backends](for_developers/backends.md)
 
 -----------
 

guide/src/cli/README.md

@@ -1,4 +1,4 @@
-# Command Line Tool
+# Command-line tool
 
 The `mdbook` command-line tool is used to create and build books.
 After you have [installed](../guide/installation.md) `mdbook`, you can run the `mdbook help` command in your terminal to view the available commands.

guide/src/continuous-integration.md

@@ -1,4 +1,4 @@
-# Running `mdbook` in Continuous Integration
+# Running `mdbook` in continuous integration
 
 There are a variety of services such as [GitHub Actions] or [GitLab CI/CD] which can be used to test and deploy your book automatically.
 

guide/src/for_developers/README.md

@@ -1,4 +1,4 @@
-# For Developers
+# For developers
 
 While `mdbook` is mainly used as a command line tool, you can also import the
 underlying libraries directly and use those to manage a book. It also has a fairly
@@ -14,7 +14,7 @@ The two main ways a developer can hook into the book's build process is via,
 - [Preprocessors](preprocessors.md)
 - [Alternative Backends](backends.md)
 
-## The Build Process
+## The build process
 
 The process of rendering a book project goes through several steps.
 
@@ -27,7 +27,7 @@ The process of rendering a book project goes through several steps.
    1. Run all the preprocessors.
    2. Call the backend to render the processed result.
 
-## Using `mdbook` as a Library
+## Using `mdbook` as a library
 
 The `mdbook` binary is just a wrapper around the underlying mdBook crates,
 exposing their functionality as a command-line program. If you want to

guide/src/for_developers/backends.md

@@ -1,4 +1,4 @@
-# Alternative Backends
+# Alternative backends
 
 A "backend" is simply a program which `mdbook` will invoke during the book
 rendering process. This program is passed a JSON representation of the book and
@@ -10,7 +10,7 @@ See [Configuring Renderers](../format/configuration/renderers.md) for more infor
 The community has developed several backends.
 See the [Third Party Plugins] wiki page for a list of available backends.
 
-## Setting Up
+## Setting up
 
 This page will step you through creating your own alternative backend in the form
 of a simple word counting program. Although it will be written in Rust, there's
@@ -50,7 +50,7 @@ fn main() {
 > It is recommended that backends use the [`semver`] crate to inspect this field
 > and emit a warning if there may be a compatibility issue.
 
-## Inspecting the Book
+## Inspecting the book
 
 Now our backend has a copy of the book, lets count how many words are in each
 chapter!
@@ -79,7 +79,7 @@ fn count_words(ch: &Chapter) -> usize {
 ```
 
 
-## Enabling the Backend
+## Enabling the backend
 
 Now we've got the basics running, we want to actually use it. First, install the
 program.
@@ -216,7 +216,7 @@ and then add a check to make sure we skip ignored chapters.
 ```
 
 
-## Output and Signalling Failure
+## Output and signalling failure
 
 While it's nice to print word counts to the terminal when a book is built, it
 might also be a good idea to output them to a file somewhere. `mdbook` tells a
@@ -319,7 +319,7 @@ generation or a warning).
 All environment variables are passed through to the backend, allowing you to use
 the usual `RUST_LOG` to control logging verbosity.
 
-## Wrapping Up
+## Wrapping up
 
 Although contrived, hopefully this example was enough to show how you'd create
 an alternative backend for `mdbook`. If you feel it's missing something, don't

guide/src/for_developers/preprocessors.md

@@ -10,7 +10,7 @@ the book. Possible use cases are:
 
 See [Configuring Preprocessors](../format/configuration/preprocessors.md) for more information about using preprocessors.
 
-## Hooking Into MDBook
+## Hooking into MDBook
 
 MDBook uses a fairly simple mechanism for discovering third party plugins.
 A new table is added to `book.toml` (e.g. `[preprocessor.foo]` for the `foo`
@@ -43,7 +43,7 @@ be adapted for other preprocessors.
 ```
 </details>
 
-## Hints For Implementing A Preprocessor
+## Hints for implementing a preprocessor
 
 By pulling in `mdbook-preprocessor` as a library, preprocessors can have access to the
 existing infrastructure for dealing with books.

guide/src/format/configuration/environment-variables.md

@@ -1,4 +1,4 @@
-# Environment Variables
+# Environment variables
 
 All configuration values can be overridden from the command line by setting the
 corresponding environment variable. Because many operating systems restrict

guide/src/format/configuration/general.md

@@ -1,4 +1,4 @@
-# General Configuration
+# General configuration
 
 You can configure the parameters for your book in the ***book.toml*** file.
 

guide/src/format/configuration/preprocessors.md

@@ -23,7 +23,7 @@ For information on how to create a new preprocessor, see the [Preprocessors for
 [Third Party Plugins]: https://github.com/rust-lang/mdBook/wiki/Third-party-plugins
 [Preprocessors for Developers]: ../../for_developers/preprocessors.md
 
-## Custom Preprocessor Configuration
+## Custom preprocessor configuration
 
 Preprocessors can be added by including a `preprocessor` table in `book.toml` with the name of the preprocessor.
 For example, if you have a preprocessor called `mdbook-example`, then you can include it with:
@@ -42,7 +42,7 @@ For example, if our example preprocessor needed some extra configuration options
 some-extra-feature = true
 ```
 
-## Locking a Preprocessor dependency to a renderer
+## Locking a preprocessor dependency to a renderer
 
 You can explicitly specify that a preprocessor should run for a renderer by
 binding the two together.
@@ -52,7 +52,7 @@ binding the two together.
 renderers = ["html"]  # example preprocessor only runs with the HTML renderer
 ```
 
-## Provide Your Own Command
+## Provide your own command
 
 By default when you add a `[preprocessor.foo]` table to your `book.toml` file,
 `mdbook` will try to invoke the `mdbook-foo` executable. If you want to use a
@@ -76,7 +76,7 @@ optional = true
 
 This demotes the error to a warning.
 
-## Require A Certain Order
+## Require a certain order
 
 The order in which preprocessors are run can be controlled with the `before` and `after` fields.
 For example, suppose you want your `linenos` preprocessor to process lines that may have been `{{#include}}`d; then you want it to run after the built-in `links` preprocessor, which you can require using either the `before` or `after` field:

guide/src/format/configuration/renderers.md

@@ -318,7 +318,7 @@ This will generate an HTML page which will automatically redirect to the given l
 
 When fragment redirects are specified, the page must use JavaScript to redirect to the correct location. This is useful if you rename or move a section header. Fragment redirects work with existing pages and deleted pages.
 
-## Markdown Renderer
+## Markdown renderer
 
 The Markdown renderer will run preprocessors and then output the resulting
 Markdown. This is mostly useful for debugging preprocessors, especially in

guide/src/format/markdown.md

@@ -6,7 +6,7 @@ or [try out](https://spec.commonmark.org/dingus/) CommonMark in real time. A com
 this documentation, but below is a high level overview of some of the basics. For a more in-depth experience, check out the
 [Markdown Guide](https://www.markdownguide.org).
 
-## Text and Paragraphs
+## Text and paragraphs
 
 Text is rendered relatively predictably: 
 

guide/src/format/mathjax.md

@@ -1,4 +1,4 @@
-# MathJax Support
+# MathJax support
 
 mdBook has optional support for math equations through
 [MathJax](https://www.mathjax.org/).

guide/src/format/mdbook.md

@@ -71,7 +71,7 @@ nothidden():
 ```
 ~~~
 
-## Rust Playground
+## Rust playground
 
 Rust language code blocks will automatically get a play button (<i class="fa fa-play"></i>) which will execute the code and display the output just below the code block.
 This works by sending the code to the [Rust Playground].

guide/src/format/theme/editor.md

@@ -32,7 +32,7 @@ fn main() {
 
 Note the new `Undo Changes` button in the editable playgrounds.
 
-## Customizing the Editor
+## Customizing the editor
 
 By default, the editor is the [Ace](https://ace.c9.io/) editor, but, if desired,
 the functionality may be overridden by providing a different folder:

guide/src/format/theme/index-hbs.md

@@ -38,7 +38,7 @@ Here is a list of the properties that are exposed:
   containing all the chapters of the book. It is used for example to construct
   the table of contents (sidebar).
 
-## Handlebars Helpers
+## Handlebars helpers
 
 In addition to the properties you can access, there are some handlebars helpers
 at your disposal.

guide/src/format/theme/syntax-highlighting.md

@@ -1,4 +1,4 @@
-# Syntax Highlighting
+# Syntax highlighting
 
 mdBook uses [Highlight.js](https://highlightjs.org) with a custom theme
 for syntax highlighting.

guide/src/guide/README.md

@@ -1,4 +1,4 @@
-# User Guide
+# User guide
 
 This user guide provides an introduction to basic concepts of using mdBook.
 

guide/src/guide/creating.md

@@ -1,4 +1,4 @@
-# Creating a Book
+# Creating a book
 
 Once you have the `mdbook` CLI tool installed, you can use it to create and render a book.
 

guide/src/guide/reading.md

@@ -1,4 +1,4 @@
-# Reading Books
+# Reading books
 
 This chapter gives an introduction on how to interact with a book produced by mdBook.
 This assumes you are reading an HTML book.