This commit adds support for theme composition and inheritance in Hugo.
With this, it helps thinking about a theme as a set of ordered components:
```toml
theme = ["my-shortcodes", "base-theme", "hyde"]
```
The theme definition example above in `config.toml` creates a theme with the 3 components with presedence from left to right.
So, Hugo will, for any given file, data entry etc., look first in the project, and then in `my-shortcode`, `base-theme` and lastly `hyde`.
Hugo uses two different algorithms to merge the filesystems, depending on the file type:
* For `i18n` and `data` files, Hugo merges deeply using the translation id and data key inside the files.
* For `static`, `layouts` (templates) and `archetypes` files, these are merged on file level. So the left-most file will be chosen.
The name used in the `theme` definition above must match a folder in `/your-site/themes`, e.g. `/your-site/themes/my-shortcodes`. There are plans to improve on this and get a URL scheme so this can be resolved automatically.
Also note that a component that is part of a theme can have its own configuration file, e.g. `config.toml`. There are currently some restrictions to what a theme component can configure:
* `params` (global and per language)
* `menu` (global and per language)
* `outputformats` and `mediatypes`
The same rules apply here: The left-most param/menu etc. with the same ID will win. There are some hidden and experimental namespace support in the above, which we will work to improve in the future, but theme authors are encouraged to create their own namespaces to avoid naming conflicts.
A final note: Themes/components can also have a `theme` definition in their `config.toml` and similar, which is the "inheritance" part of this commit's title. This is currently not supported by the Hugo theme site. We will have to wait for some "auto dependency" feature to be implemented for that to happen, but this can be a powerful feature if you want to create your own theme-variant based on others.
Fixes#4460Fixes#4450
A sample config:
```toml
defaultContentLanguage = "en"
defaultContentLanguageInSubdir = true
[Languages]
[Languages.en]
weight = 10
title = "In English"
languageName = "English"
contentDir = "content/english"
[Languages.nn]
weight = 20
title = "På Norsk"
languageName = "Norsk"
contentDir = "content/norwegian"
```
The value of `contentDir` can be any valid path, even absolute path references. The only restriction is that the content dirs cannot overlap.
The content files will be assigned a language by
1. The placement: `content/norwegian/post/my-post.md` will be read as Norwegian content.
2. The filename: `content/english/post/my-post.nn.md` will be read as Norwegian even if it lives in the English content folder.
The content directories will be merged into a big virtual filesystem with one simple rule: The most specific language file will win.
This means that if both `content/norwegian/post/my-post.md` and `content/english/post/my-post.nn.md` exists, they will be considered duplicates and the version inside `content/norwegian` will win.
Note that translations will be automatically assigned by Hugo by the content file's relative placement, so `content/norwegian/post/my-post.md` will be a translation of `content/english/post/my-post.md`.
If this does not work for you, you can connect the translations together by setting a `translationKey` in the content files' front matter.
Fixes#4523Fixes#4552Fixes#4553
This is in heavy use in rendering, so this makes a difference:
```bash
benchmark old ns/op new ns/op delta
BenchmarkSiteBuilding/TOML,num_langs=1,num_pages=500,tags_per_page=5,shortcodes,render-4 124551144 107743429 -13.49%
benchmark old allocs new allocs delta
BenchmarkSiteBuilding/TOML,num_langs=1,num_pages=500,tags_per_page=5,shortcodes,render-4 528684 435118 -17.70%
benchmark old bytes new bytes delta
BenchmarkSiteBuilding/TOML,num_langs=1,num_pages=500,tags_per_page=5,shortcodes,render-4 53306848 45147832 -15.31%
```
This commit moves almost all of the template functions into separate
packages under tpl/ and adds a namespace framework. All changes should
be backward compatible for end users, as all existing function names in
the template funcMap are left intact.
Seq and DoArithmatic have been moved out of the helpers package and into
template namespaces.
Most of the tests involved have been refactored, and many new tests have
been written. There's still work to do, but this is a big improvement.
I got a little overzealous and added some new functions along the way:
- strings.Contains
- strings.ContainsAny
- strings.HasSuffix
- strings.TrimPrefix
- strings.TrimSuffix
Documentation is forthcoming.
Fixes#3042
