Filter by `None`/`Any` for labels in issues/mrs API

By using the parameters `?labels=None|Any` the user can filter
issues/mrs from the API that has `none/any` label.

Affected endpoints are:

- /api/issues
- /api/projects/:id/issues
- /api/groups/:id/issues
- /api/merge_requests
- /api/projects/:id/merge_requests
- /api/groups/:id/merge_requests

2 files changed, 6 insertions, 6 deletions

diff --git a/doc/api/issues.md b/doc/api/issues.md
index 0e97d9ea6f5..6a99c52234d 100644
--- a/doc/api/issues.md
+++ b/doc/api/issues.md
@@ -36,7 +36,7 @@ GET /issues?my_reaction_emoji=star
 | Attribute           | Type             | Required   | Description                                                                                                                                         |
 | ------------------- | ---------------- | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `state`             | string           | no         | Return all issues or just those that are `opened` or `closed`                                                                                       |
-| `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `No+Label` lists all issues with no labels                         |
+| `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `None` lists all issues with no labels. `Any` lists all issues with at least one label. `No+Label` (Deprecated) lists all issues with no labels. Predefined names are case-insensitive. |
 | `milestone`         | string           | no         | The milestone title. `None` lists all issues with no milestone. `Any` lists all issues that have an assigned milestone.                             |
 | `scope`             | string           | no         | Return issues for the given scope: `created_by_me`, `assigned_to_me` or `all`. Defaults to `created_by_me`<br> For versions before 11.0, use the now deprecated `created-by-me` or `assigned-to-me` scopes instead.<br> _([Introduced][ce-13004] in GitLab 9.5. [Changed to snake_case][ce-18935] in GitLab 11.0)_ |
 | `author_id`         | integer          | no         | Return issues created by the given user `id`. Combine with `scope=all` or `scope=assigned_to_me`. _([Introduced][ce-13004] in GitLab 9.5)_          |
@@ -149,7 +149,7 @@ GET /groups/:id/issues?my_reaction_emoji=star
 | ------------------- | ---------------- | ---------- | ----------------------------------------------------------------------------------------------------------------------------- |
 | `id`                | integer/string   | yes        | The ID or [URL-encoded path of the group](README.md#namespaced-path-encoding) owned by the authenticated user                 |
 | `state`             | string           | no         | Return all issues or just those that are `opened` or `closed`                                                                 |
-| `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `No+Label` lists all issues with no labels   |
+| `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `None` lists all issues with no labels. `Any` lists all issues with at least one label. `No+Label` (Deprecated) lists all issues with no labels. Predefined names are case-insensitive. |
 | `iids[]`            | Array[integer]   | no         | Return only the issues having the given `iid`                                                                                 |
 | `milestone`         | string           | no         | The milestone title. `None` lists all issues with no milestone. `Any` lists all issues that have an assigned milestone.       |
 | `scope`             | string           | no         | Return issues for the given scope: `created_by_me`, `assigned_to_me` or `all`.<br> For versions before 11.0, use the now deprecated `created-by-me` or `assigned-to-me` scopes instead.<br> _([Introduced][ce-13004] in GitLab 9.5. [Changed to snake_case][ce-18935] in GitLab 11.0)_ |
@@ -264,7 +264,7 @@ GET /projects/:id/issues?my_reaction_emoji=star
 | `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user               |
 | `iids[]`            | Array[integer]   | no         | Return only the milestone having the given `iid`                                                                              |
 | `state`             | string           | no         | Return all issues or just those that are `opened` or `closed`                                                                 |
-| `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `No+Label` lists all issues with no labels   |
+| `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `None` lists all issues with no labels. `Any` lists all issues with at least one label. `No+Label` (Deprecated) lists all issues with no labels. Predefined names are case-insensitive. |
 | `milestone`         | string           | no         | The milestone title. `None` lists all issues with no milestone. `Any` lists all issues that have an assigned milestone.       |
 | `scope`             | string           | no         | Return issues for the given scope: `created_by_me`, `assigned_to_me` or `all`.<br> For versions before 11.0, use the now deprecated `created-by-me` or `assigned-to-me` scopes instead.<br> _([Introduced][ce-13004] in GitLab 9.5. [Changed to snake_case][ce-18935] in GitLab 11.0)_ |
 | `author_id`         | integer          | no         | Return issues created by the given user `id` _([Introduced][ce-13004] in GitLab 9.5)_                                         |
diff --git a/doc/api/merge_requests.md b/doc/api/merge_requests.md
index 9cb3f0d9c0c..da70c74c4ce 100644
--- a/doc/api/merge_requests.md
+++ b/doc/api/merge_requests.md
@@ -35,7 +35,7 @@ Parameters:
 | `sort`              | string   | no       | Return requests sorted in `asc` or `desc` order. Default is `desc`                                                     |
 | `milestone`         | string   | no       | Return merge requests for a specific milestone. `None` returns merge requests with no milestone. `Any` returns merge requests that have an assigned milestone. |
 | `view`              | string   | no       | If `simple`, returns the `iid`, URL, title, description, and basic state of merge request                              |
-| `labels`            | string   | no       | Return merge requests matching a comma separated list of labels                                                        |
+| `labels`            | string   | no       | Return merge requests matching a comma separated list of labels. `None` lists all merge requests with no labels. `Any` lists all merge requests with at least one label. `No+Label` (Deprecated) lists all merge requests with no labels. Predefined names are case-insensitive. |
 | `created_after`     | datetime | no       | Return merge requests created on or after the given time                                                               |
 | `created_before`    | datetime | no       | Return merge requests created on or before the given time                                                              |
 | `updated_after`     | datetime | no       | Return merge requests updated on or after the given time                                                               |
@@ -170,7 +170,7 @@ Parameters:
 | `sort`              | string         | no       | Return requests sorted in `asc` or `desc` order. Default is `desc`                                                             |
 | `milestone`         | string         | no       | Return merge requests for a specific milestone. `None` returns merge requests with no milestone. `Any` returns merge requests that have an assigned milestone. |
 | `view`              | string         | no       | If `simple`, returns the `iid`, URL, title, description, and basic state of merge request                                      |
-| `labels`            | string         | no       | Return merge requests matching a comma separated list of labels                                                                |
+| `labels`            | string         | no       | Return merge requests matching a comma separated list of labels. `None` lists all merge requests with no labels. `Any` lists all merge requests with at least one label. `No+Label` (Deprecated) lists all merge requests with no labels. Predefined names are case-insensitive. |
 | `created_after`     | datetime       | no       | Return merge requests created on or after the given time                                                                       |
 | `created_before`    | datetime       | no       | Return merge requests created on or before the given time                                                                      |
 | `updated_after`     | datetime       | no       | Return merge requests updated on or after the given time                                                                       |
@@ -294,7 +294,7 @@ Parameters:
 | `sort`              | string         | no       | Return merge requests sorted in `asc` or `desc` order. Default is `desc`                                                       |
 | `milestone`         | string         | no       | Return merge requests for a specific milestone. `None` returns merge requests with no milestone. `Any` returns merge requests that have an assigned milestone. |
 | `view`              | string         | no       | If `simple`, returns the `iid`, URL, title, description, and basic state of merge request                                      |
-| `labels`            | string         | no       | Return merge requests matching a comma separated list of labels                                                                |
+| `labels`            | string         | no       | Return merge requests matching a comma separated list of labels. `None` lists all merge requests with no labels. `Any` lists all merge requests with at least one label. `No+Label` (Deprecated) lists all merge requests with no labels. Predefined names are case-insensitive. |
 | `created_after`     | datetime       | no       | Return merge requests created on or after the given time                                                                       |
 | `created_before`    | datetime       | no       | Return merge requests created on or before the given time                                                                      |
 | `updated_after`     | datetime       | no       | Return merge requests updated on or after the given time                                                                       |