Configuration file & Configuration inheritance

Problem

Assume that I am creating the book as a PDF file using the mdbook-pdf plugin and verifying all of the links with the mdbook-linkcheck plugin.
The process of validating links and creating the PDF file, which is mostly required only for book releases, takes a significant amount of time, and the development process (using mdbook serve) suffers because the book has to be rebuilt for every change.
Removing [output.pdf] and [output.linkcheck] manually from book.toml is the only way to resolve this, and don't forget to add them back before committing!
The entire process is excessively error-prone and tedious.

It would be really useful if mdbook had a command line parameter for customizing the configuration file.
Furthermore, supports configuration inheritance to prevent needless duplications. This means that all common configurations (such as title, description, author, etc.) can be contained in a base configuration file, and the latter can be extended by additional configuration files based on the context (like development and release).

The entire feature should be similar to TypeScript extends.

Proposed Solution

1. Custom configuration file

   If omitted defaults to book.toml

   mdbook --config path/to/book.toml
   

2. Configuration inheritance

   book.dev.toml

   [book]
   title = "Book"
   
   # ...
   

   book.toml

   extends = "./book.dev.toml"
   
   [output.pdf]
   
   [output.linkcheck]
   follow-web-links = true
   warning-policy = "error"
   

Notes

No response

Start with the mdbook command and the existing book.toml loading behavior, then compare the proposed book.dev.toml and book.toml examples. Define how --config selects a file and how extends combines inherited and context-specific settings; done means development and release configurations can be used without editing book.toml manually.