Add collections options

website/site/content/docs/configuration-options.md

@@ -11,6 +11,7 @@ To see working configuration examples, you can [start from a template](https://w
 
 You can find details about all configuration options below. Note that [YAML syntax](https://en.wikipedia.org/wiki/YAML#Basic_components) allows lists and objects to be written in block or inline style, and the code samples below include a mix of both.
 
+
 ## Backend
 
 *This setting is required.*
@@ -60,3 +61,87 @@ public_folder: "/images/uploads"
 Based on the settings above, if a user used an image widget field called `avatar` to upload and select an image called `philosoraptor.png`, the image would be saved to the repository at `/static/images/uploads/philosoraptor.png`, and the `avatar` field for the file would be set to `/images/uploads/philosoraptor.png`.
 
 
+## Collections
+
+*This setting is required.*
+
+The `collections` setting is the heart of your Netlify CMS configuration, as it determines how content types and editor fields in the UI generate files and content in your repository. Each collection you configure displays in the left sidebar of the Content page of the editor UI, in the order they are entered into `config.yml`.
+
+`collections` accepts a list of collection objects, each with the following options:
+
+- `name` (required): unique identifier for the collection, used as the key when referenced in other contexts (like the [relation widget](https://www.netlifycms.org/docs/widgets/#relation))
+- `Label`: label for the collection in the editor UI; defaults to the value of `name`
+- `file` or `folder` (requires one of these): specifies the collection type and location; details in [Collection Types](https://www.netlifycms.org/docs/collection-types)
+- `filter`: optional filter for `folder` collections; details in [Collection Types](https://www.netlifycms.org/docs/collection-types)
+- `create`: for `folder` collections only; `true` allows users to create new items in the collection; defaults to `false`
+- `delete`: `false` prevents users from deleting items in a collection; defaults to `true`
+- `extension`: see detailed description below
+- `format`: see detailed description below
+- `slug`: see detailed description below
+- `fields` (required): see detailed description below
+
+The last few options require more detailed information.
+
+### `extension` and `format`
+
+These settings determine how collection files are parsed and saved. Both are optional—Netlify CMS will attempt to infer your settings based on existing items in the collection. If your collection is empty, or you'd like more control, you can set these fields explicitly.
+
+`extension` determines the file extension searched for when finding existing entries in a folder collection determines the file extension saved for new collection items. It accepts the following values: `yml`, `yaml`, `toml`, `json`, `md`, `markdown`, `html`.
+
+You may also specify a custom `extention` not included in the list above, as long as the collection files can be parsed and saved in one of the supported formats below.
+
+`format` determines how collection files are parsed and saved. It will be inferred if the `extension` field or existing collection file extensions match one of the supported extensions above. It accepts the following values:
+
+- `yml` or `yaml`: parses and saves files as YAML-formatted data files; saves with `yml` extension by default
+- `toml`: parses and saves files as TOML-formatted data files; saves with `toml` extension by default
+- `json`: parses and saves files as JSON-formatted data files; saves with `json` extension by default
+- `frontmatter`: parses files and saves files with data frontmatter followed by an unparsed body text (edited using a `body` field); saves with `md` extension by default; default for collections that can't be inferred
+
+Collections with `frontmatter` format (either inferred or explicitly set) can parse files with frontmatter in YAML, TOML, or JSON format. On saving, however, they will currently be saved with YAML frontmatter. (Follow [Issue #563](https://github.com/netlify/netlify-cms/issues/563)) to see when this changes.)
+
+
+### `slug`
+
+For folder collections where users can create new items, the `slug` option specifies a template for generating new filenames based on a file's creation date and `title` field. (This means that all collections with `create: true` must have a `title` field.)
+
+**Available template tags:**
+
+- `{{slug}}`: a url-safe version of the `title` field for the file
+- `{{year}}`: 4-digit year of the file creation date
+- `{{month}}`: 2-digit month of the file creation date
+- `{{day}}`: 2-digit day of the month of the file creation date
+
+**Example:**
+
+```yaml
+slug: "{{year}}-{{month}}-{{day}}_{{slug}}"
+```
+
+### `fields`
+
+The `fields` option maps editor UI widgets to field-value pairs in the saved file. The order of the fields in `config.yml` determines their order in the editor UI and in the saved file.
+
+`fields` accepts a list of collection objects, each with the following options:
+
+- `name` (required): unique identifier for the field, used as the key when referenced in other contexts (like the [relation widget](https://www.netlifycms.org/docs/widgets/#relation))
+- `label`: label for the field in the editor UI; defaults to the value of `name`
+- `widget`: defines editor UI and inputs and file field data types; details in [Widgets](https://www.netlifycms.org/docs/widgets)
+- `default`: specify a default value for a field; available for most widget types (see [Widgets](https://www.netlifycms.org/docs/widgets) for details on each widget type)
+- `required`: specify as `false` to make a field optional; defaults to `true`
+- `pattern`: add field validation by specifying a list with a regex pattern and an error message; more extensive validation can be achieved with [custom widgets](https://www.netlifycms.org/docs/custom-widgets/#advanced-field-validation)
+
+In files with frontmatter, one field should be named `body`. This special field represents the section of the document (usually markdown) that comes after the frontmatter.
+
+**Example:**
+
+```yaml
+fields:
+  - label: "Title"
+    name: "title"
+    widget: "string"
+    pattern: ['.{10,}', "Must have at least 20 characters"]
+  - {label: "Layout", name: "layout", widget: "hidden", default: "blog"}
+  - {label: "Featured Image", name: "thumbnail", widget: "image", required: false}
+  - {label: "Body", name: "body", widget: "markdown"}
+```
+