The main motivation behind this is simplicity and correctnes, but the new small config library is also faster:
```
BenchmarkDefaultConfigProvider/Viper-16 252418 4546 ns/op 2720 B/op 30 allocs/op
BenchmarkDefaultConfigProvider/Custom-16 450756 2651 ns/op 1008 B/op 6 allocs/op
```
Fixes#8633Fixes#8618Fixes#8630
Updates #8591Closes#6680Closes#5192
This change is mostly motivated to get a more stable CI build (we're building the Hugo site there, with Instagram and Twitter shortcodes sometimes failing).
Fixes#7866
This is preparation for #6041.
For historic reasons, the code for bulding the section tree and the taxonomies were very much separate.
This works, but makes it hard to extend, maintain, and possibly not so fast as it could be.
This simplification also introduces 3 slightly breaking changes, which I suspect most people will be pleased about. See referenced issues:
This commit also switches the radix tree dependency to a mutable implementation: github.com/armon/go-radix.
Fixes#6154Fixes#6153Fixes#6152
This commit implements Hugo Modules.
This is a broad subject, but some keywords include:
* A new `module` configuration section where you can import almost anything. You can configure both your own file mounts nd the file mounts of the modules you import. This is the new recommended way of configuring what you earlier put in `configDir`, `staticDir` etc. And it also allows you to mount folders in non-Hugo-projects, e.g. the `SCSS` folder in the Bootstrap GitHub project.
* A module consists of a set of mounts to the standard 7 component types in Hugo: `static`, `content`, `layouts`, `data`, `assets`, `i18n`, and `archetypes`. Yes, Theme Components can now include content, which should be very useful, especially in bigger multilingual projects.
* Modules not in your local file cache will be downloaded automatically and even "hot replaced" while the server is running.
* Hugo Modules supports and encourages semver versioned modules, and uses the minimal version selection algorithm to resolve versions.
* A new set of CLI commands are provided to manage all of this: `hugo mod init`, `hugo mod get`, `hugo mod graph`, `hugo mod tidy`, and `hugo mod vendor`.
All of the above is backed by Go Modules.
Fixes#5973Fixes#5996Fixes#6010Fixes#5911Fixes#5940Fixes#6074Fixes#6082Fixes#6092
