The main topic of this commit is that you can now index fragments (content heading identifiers) when calling `.Related`.
You can do this by:
* Configure one or more indices with type `fragments`
* The name of those index configurations maps to an (optional) front matter slice with fragment references. This allows you to link
page<->fragment and page<->page.
* This also will index all the fragments (heading identifiers) of the pages.
It's also possible to use type `fragments` indices in shortcode, e.g.:
```
{{ $related := site.RegularPages.Related .Page }}
```
But, and this is important, you need to include the shortcode using the `{{<` delimiter. Not doing so will create infinite loops and timeouts.
This commit also:
* Adds two new methods to Page: Fragments (can also be used to build ToC) and HeadingsFiltered (this is only used in Related Content with
index type `fragments` and `enableFilter` set to true.
* Consolidates all `.Related*` methods into one, which takes either a `Page` or an options map as its only argument.
* Add `context.Context` to all of the content related Page API. Turns out it wasn't strictly needed for this particular feature, but it will
soon become usefil, e.g. in #9339.
Closes#10711
Updates #9339
Updates #10725
* Add file context to minifier errors when publishing
* Misc fixes (see issues)
* Allow custom server error template in layouts/server/error.html
To get to this, this commit also cleans up and simplifies the code surrounding errors and files. This also removes the usage of `github.com/pkg/errors`, mostly because of https://github.com/pkg/errors/issues/223 -- but also because most of this is now built-in to Go.
Fixes#9852Fixes#9857Fixes#9863
I have had this living in a separate branch for now, but we need this in the main branch sooner rather than later.
One big advantage of this is that integration tests can live in any package, not just hugolib.
Expand the text in the init timeout message to give the reader more hints as to what may be causing the issue.
The current error sent me on a wild goose chase trying to debug my shortcodes, but it turned out that the issue was just that I wasn't caching my resources/ directory on my build server. Once I found this blog post, I solved the issue in minutes:
https://www.henriksommerfeld.se/hugo-timeout-not-a-circular-loop-in-shortcode/
Googling the error message yields several additional posts from users who focus on loops in their shortcode when the problem seems to be overly-expensive builds.
The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue #5074, "pages from other data sources".
But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.
Most notable changes:
* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
This improves the taxonomy template `.Title` situation and make common template constructs much simpler.
See #5074Fixes#5763Fixes#5758Fixes#5090Fixes#5204Fixes#4695Fixes#5607Fixes#5707Fixes#5719Fixes#3113Fixes#5706Fixes#5767Fixes#5723Fixes#5769Fixes#5770Fixes#5771Fixes#5759Fixes#5776Fixes#5777Fixes#5778
