Use the `Formatted Date` meta header to explicitly set a page's formatted date (i.e. `$meta['date_formatted']`), and `Time` to set `$meta['time']`. Use the `Hidden` meta header to manually hide a page (the page is still accessible, but won't show up in the pages list). Note the difference between `$pageData['hidden']` and `$pageData['meta']['hidden']`.
AbstractPicoPlugin::$enabled now defaults to NULL what leaves the decision whether a plugin should be enabled or disabled by default up to Pico (precisely AbstractPicoPlugin::triggerEvent()). If all dependencies of a plugin are fulfilled, Pico enables the plugin by default. Otherwise the plugin is silently disabled (this was the behavior when AbstractPicoPlugin::$enabled was set to TRUE previously).
If a plugin should never be disabled *silently* (e.g. when dealing with security-relevant stuff like access control, or similar), set AbstractPicoPlugin::$enabled to TRUE. If Pico can't fulfill all the plugin's dependencies, it will throw an RuntimeException.
If a plugin rather does some "crazy stuff" a user should really be aware of before using it, you can set AbstractPicoPlugin::$enabled to FALSE. The user will then have to enable the plugin manually. However, if another plugin depends on this plugin, it might get enabled silently nevertheless.
No matter what, the user can always explicitly enable or disable a plugin in Pico's config.
We recommend plugin developers to use templates when serving HTML contents (like the UI of PicoAdmin), however, by supporting multiple file extensions for themes, we make it pretty hard to overwrite a plugin's template with a theme. As always, we preserve BC using PicoDeprecated.
Pico's page tree is a list of all the tree's branches (no matter the depth). Thus, by iterating a array element, you get the nodes of a given branch. All leaf nodes do represent a page, but inner nodes may or may not represent a page (e.g. if there's a `sub/page.md`, but neither a `sub/index.md` nor a `sub.md`, the inner node `sub`, that is the parent of the `sub/page` node, represents no page itself).
A page's file path describes its node's path in the tree (e.g. the page `sub/page.md` is represented by the `sub/page` node, thus a child of the `sub` node and a element of the `sub` branch). However, the index page of a folder (e.g. `sub/index.md`), is *not* a node of the `sub` branch, but rather of the `/` branch. The page's node is not `sub/index`, but `sub`. If two pages are described by the same node (e.g. if both a `sub/index.md` and a `sub.md` exist), the index page takes precedence. Pico's main index page (i.e. `index.md`) is represented by the tree's root node `/` and a special case: it is the only node of the `` (i.e. the empty string) branch.
A node is represented by an array with the keys `id`, `page` and `children`. The `id` key contains a string with the node's name. If the node represents a page, the `page` key is a reference to the page's data array. If the node is a inner node, the `children` key is a reference to its matching branch (i.e. a list of the node's children). The order of a node's children matches the order in Pico's pages array.
If you want to walk the whole page tree, start with the tree's root node at `$pageTree[""]["/"]`. The root node's `children` key is a reference to the `/` branch at `$pageTree["/"]`, that is a list of the root node's direct child nodes and their siblings.
You MUST NOT iterate the page tree itself (i.e. the list of the tree's branches), its order is undefined and the array will be replaced by a non-iterable data structure with Pico 3.0.
Don't lower unregistered meta headers on the first level unsolicited (e.g. `SomeNotRegisteredKey: foobar` in the YAML Frontmatter should result in `['SomeNotRegisteredKey']`, not `['somenotregisteredkey']`). Furthermore, Pico no longer compares registered meta headers in a case-insensitive manner. However, you can now register multiple search strings that are used to find a registered meta header. This is achieved by flipping the meta headers array: Pico 2.0 uses the array key to search for a meta value and the array value to store the found meta value. Previously it was the other way round (what didn't make much sense...).
The performance vs. error-proneness trade-off doesn't justify this additional complexity. This is Pico 2.0, we always try to minimize BC-breaking changes, but we're breaking BC anyway by loading plugins from plugins/<plugin name>/<plugin name>.php only...
You can now explicitly specify both the `date_formatted` and `time` meta values to overwrite Pico's page date handling. Specifying `time` doesn't make much sense in general, however, specifying `date_formatted` allows you to use `{{ meta.date_formatted }}` on all systems, even those where `strftime()` doesn't work as wished
