Use ResourceLabelEvent for tracking label changes

2 files changed, 176 insertions, 0 deletions

diff --git a/doc/api/README.md b/doc/api/README.md
index e2a6e87a2c3..1738d4fae5c 100644
--- a/doc/api/README.md
+++ b/doc/api/README.md
@@ -40,6 +40,7 @@ following locations:
 - [Namespaces](namespaces.md)
 - [Notes](notes.md) (comments)
 - [Discussions](discussions.md) (threaded comments)
+- [Resource Label Events](resource_label_events.md)
 - [Notification settings](notification_settings.md)
 - [Open source license templates](templates/licenses.md)
 - [Pages Domains](pages_domains.md)
diff --git a/doc/api/resource_label_events.md b/doc/api/resource_label_events.md
new file mode 100644
index 00000000000..33e4821ccf4
--- /dev/null
+++ b/doc/api/resource_label_events.md
@@ -0,0 +1,175 @@
+# Resource label events API
+
+Resource label events keep track about who, when, and which label was added or removed to an issuable.
+
+## Issues
+
+### List project issue label events
+
+Gets a list of all label events for a single issue.
+
+```
+GET /projects/:id/issues/:issue_iid/resource_label_events
+```
+
+| Attribute           | Type             | Required   | Description  |
+| ------------------- | ---------------- | ---------- | ------------ |
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`         | integer          | yes        | The IID of an issue |
+
+```json
+[
+  {
+    "id": 142,
+    "user": {
+      "id": 1,
+      "name": "Administrator",
+      "username": "root",
+      "state": "active",
+      "avatar_url": "https://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
+      "web_url": "http://gitlab.example.com/root"
+    },
+    "created_at": "2018-08-20T13:38:20.077Z",
+    "resource_type": "Issue",
+    "resource_id": 253,
+    "label": {
+      "id": 73,
+      "name": "a1",
+      "color": "#34495E",
+      "description": ""
+    },
+    "action": "add"
+  },
+  {
+    "id": 143,
+    "user": {
+      "id": 1,
+      "name": "Administrator",
+      "username": "root",
+      "state": "active",
+      "avatar_url": "https://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
+      "web_url": "http://gitlab.example.com/root"
+    },
+    "created_at": "2018-08-20T13:38:20.077Z",
+    "resource_type": "Issue",
+    "resource_id": 253,
+    "label": {
+      "id": 74,
+      "name": "p1",
+      "color": "#0033CC",
+      "description": ""
+    },
+    "action": "remove"
+  }
+]
+```
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/resource_label_events
+```
+
+### Get single issue label event
+
+Returns a single label event for a specific project issue
+
+```
+GET /projects/:id/issues/:issue_iid/resource_label_events/:resource_label_event_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`     | integer        | yes      | The IID of an issue |
+| `resource_label_event_id` | integer        | yes      | The ID of a label event |
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/resource_label_events/1
+```
+
+## Merge requests
+
+### List project merge request label events
+
+Gets a list of all label events for a single merge request.
+
+```
+GET /projects/:id/merge_requests/:merge_request_iid/resource_label_events
+```
+
+| Attribute           | Type             | Required   | Description  |
+| ------------------- | ---------------- | ---------- | ------------ |
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `merge_request_iid` | integer          | yes        | The IID of a merge request |
+
+```json
+[
+  {
+    "id": 119,
+    "user": {
+      "id": 1,
+      "name": "Administrator",
+      "username": "root",
+      "state": "active",
+      "avatar_url": "https://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
+      "web_url": "http://gitlab.example.com/root"
+    },
+    "created_at": "2018-08-20T06:17:28.394Z",
+    "resource_type": "MergeRequest",
+    "resource_id": 28,
+    "label": {
+      "id": 74,
+      "name": "p1",
+      "color": "#0033CC",
+      "description": ""
+    },
+    "action": "add"
+  },
+  {
+    "id": 120,
+    "user": {
+      "id": 1,
+      "name": "Administrator",
+      "username": "root",
+      "state": "active",
+      "avatar_url": "https://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon",
+      "web_url": "http://gitlab.example.com/root"
+    },
+    "created_at": "2018-08-20T06:17:28.394Z",
+    "resource_type": "MergeRequest",
+    "resource_id": 28,
+    "label": {
+      "id": 41,
+      "name": "project",
+      "color": "#D1D100",
+      "description": ""
+    },
+    "action": "add"
+  }
+]
+```
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/resource_label_events
+```
+
+### Get single merge request label event
+
+Returns a single label event for a specific project merge request
+
+```
+GET /projects/:id/merge_requests/:merge_request_iid/resource_label_events/:resource_label_event_id
+```
+
+Parameters:
+
+| Attribute           | Type           | Required | Description |
+| ------------------- | -------------- | -------- | ----------- |
+| `id`                | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `merge_request_iid` | integer        | yes      | The IID of a merge request |
+| `resource_label_event_id`     | integer        | yes      | The ID of a label event |
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/resource_label_events/120
+```