Merge request and commit discussions API

17 files changed, 955 insertions, 67 deletions

diff --git a/app/controllers/projects/notes_controller.rb b/app/controllers/projects/notes_controller.rb
index 86c50d88a2a..bc13b8ad7ba 100644
--- a/app/controllers/projects/notes_controller.rb
+++ b/app/controllers/projects/notes_controller.rb
@@ -33,9 +33,7 @@ class Projects::NotesController < Projects::ApplicationController
   def resolve
     return render_404 unless note.resolvable?
 
-    note.resolve!(current_user)
-
-    MergeRequests::ResolvedDiscussionNotificationService.new(project, current_user).execute(note.noteable)
+    Notes::ResolveService.new(project, current_user).execute(note)
 
     discussion = note.discussion
 
diff --git a/app/models/commit.rb b/app/models/commit.rb
index 9750e9298ec..32f3d90595a 100644
--- a/app/models/commit.rb
+++ b/app/models/commit.rb
@@ -105,6 +105,10 @@ class Commit
         end
       end
     end
+
+    def parent_class
+      ::Project
+    end
   end
 
   attr_accessor :raw
diff --git a/app/services/notes/resolve_service.rb b/app/services/notes/resolve_service.rb
new file mode 100644
index 00000000000..0db8ee809a9
--- /dev/null
+++ b/app/services/notes/resolve_service.rb
@@ -0,0 +1,9 @@
+module Notes
+  class ResolveService < ::BaseService
+    def execute(note)
+      note.resolve!(current_user)
+
+      ::MergeRequests::ResolvedDiscussionNotificationService.new(project, current_user).execute(note.noteable)
+    end
+  end
+end
diff --git a/changelogs/unreleased/jprovazn-commit-notes-api.yml b/changelogs/unreleased/jprovazn-commit-notes-api.yml
new file mode 100644
index 00000000000..4665d800ccf
--- /dev/null
+++ b/changelogs/unreleased/jprovazn-commit-notes-api.yml
@@ -0,0 +1,5 @@
+---
+title: Add discussion API for merge requests and commits
+merge_request:
+author:
+type: added
diff --git a/doc/api/discussions.md b/doc/api/discussions.md
index c341b7f2009..65e2f9d6cd9 100644
--- a/doc/api/discussions.md
+++ b/doc/api/discussions.md
@@ -1,6 +1,6 @@
 # Discussions API
 
-Discussions are set of related notes on snippets or issues.
+Discussions are set of related notes on snippets, issues, merge requests or commits.
 
 ## Issues
 
@@ -61,7 +61,8 @@ GET /projects/:id/issues/:issue_iid/discussions
         "system": false,
         "noteable_id": 3,
         "noteable_type": "Issue",
-        "noteable_iid": null
+        "noteable_iid": null,
+        "resolvable": false
       }
     ]
   },
@@ -87,7 +88,8 @@ GET /projects/:id/issues/:issue_iid/discussions
         "system": false,
         "noteable_id": 3,
         "noteable_type": "Issue",
-        "noteable_iid": null
+        "noteable_iid": null,
+        "resolvable": false
       }
     ]
   }
@@ -265,7 +267,8 @@ GET /projects/:id/snippets/:snippet_id/discussions
         "system": false,
         "noteable_id": 3,
         "noteable_type": "Snippet",
-        "noteable_id": null
+        "noteable_id": null,
+        "resolvable": false
       }
     ]
   },
@@ -291,7 +294,8 @@ GET /projects/:id/snippets/:snippet_id/discussions
         "system": false,
         "noteable_id": 3,
         "noteable_type": "Snippet",
-        "noteable_id": null
+        "noteable_id": null,
+        "resolvable": false
       }
     ]
   }
@@ -409,3 +413,574 @@ Parameters:
 ```bash
 curl --request DELETE --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions/636
 ```
+
+## Merge requests
+
+### List project merge request discussions
+
+Gets a list of all discussions for a single merge request.
+
+```
+GET /projects/:id/merge_requests/:merge_request_iid/discussions
+```
+
+| 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": "6a9c1750b37d513a43987b574953fceb50b03ce7",
+    "individual_note": false,
+    "notes": [
+      {
+        "id": 1126,
+        "type": "DiscussionNote",
+        "body": "discussion text",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-03T21:54:39.668Z",
+        "updated_at": "2018-03-03T21:54:39.668Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Merge request",
+        "noteable_iid": null,
+        "resolved": false,
+        "resolvable": true,
+        "resolved_by": null
+      },
+      {
+        "id": 1129,
+        "type": "DiscussionNote",
+        "body": "reply to the discussion",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T13:38:02.127Z",
+        "updated_at": "2018-03-04T13:38:02.127Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Merge request",
+        "noteable_iid": null,
+        "resolved": false,
+        "resolvable": true,
+        "resolved_by": null
+      }
+    ]
+  },
+  {
+    "id": "87805b7c09016a7058e91bdbe7b29d1f284a39e6",
+    "individual_note": true,
+    "notes": [
+      {
+        "id": 1128,
+        "type": null,
+        "body": "a single comment",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T09:17:22.520Z",
+        "updated_at": "2018-03-04T09:17:22.520Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Merge request",
+        "noteable_iid": null,
+        "resolved": false,
+        "resolvable": true,
+        "resolved_by": null
+      }
+    ]
+  }
+]
+```
+
+Diff comments contain also position:
+
+```json
+[
+  {
+    "id": "87805b7c09016a7058e91bdbe7b29d1f284a39e6",
+    "individual_note": false,
+    "notes": [
+      {
+        "id": 1128,
+        "type": DiffNote,
+        "body": "diff comment",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T09:17:22.520Z",
+        "updated_at": "2018-03-04T09:17:22.520Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Merge request",
+        "noteable_iid": null,
+        "position": {
+          "base_sha": "b5d6e7b1613fca24d250fa8e5bc7bcc3dd6002ef",
+          "start_sha": "7c9c2ead8a320fb7ba0b4e234bd9529a2614e306",
+          "head_sha": "4803c71e6b1833ca72b8b26ef2ecd5adc8a38031",
+          "old_path": "package.json",
+          "new_path": "package.json",
+          "position_type": "text",
+          "old_line": 27,
+          "new_line": 27
+        },
+        "resolved": false,
+        "resolvable": true,
+        "resolved_by": null
+      }
+    ]
+  }
+]
+```
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions
+```
+
+### Get single merge request discussion
+
+Returns a single discussion for a specific project merge request
+
+```
+GET /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_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 |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7
+```
+
+### Create new merge request discussion
+
+Creates a new discussion to a single project merge request. This is similar to creating
+a note but but another comments (replies) can be added to it later.
+
+```
+POST /projects/:id/merge_requests/:merge_request_iid/discussions
+```
+
+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 |
+| `body`                    | string         | yes      | The content of a discussion |
+| `created_at`              | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+| `position`                | hash           | no       | Position when creating a diff note |
+| `position[base_sha]`      | string         | yes      | Base commit SHA in the source branch |
+| `position[start_sha]`     | string         | yes      | SHA referencing commit in target branch |
+| `position[head_sha]`      | string         | yes      | SHA referencing HEAD of this merge request |
+| `position[position_type]` | string         | yes      | Type of the position reference', allowed values: 'text' or 'image' |
+| `position[new_path]`      | string         | no       | File path after change |
+| `position[new_line]`      | integer        | no       | Line number after change (for 'text' diff notes) |
+| `position[old_path]`      | string         | no       | File path before change |
+| `position[old_line]`      | integer        | no       | Line number before change (for 'text' diff notes) |
+| `position[width]`         | integer        | no       | Width of the image (for 'image' diff notes) |
+| `position[height]`        | integer        | no       | Height of the image (for 'image' diff notes) |
+| `position[x]`             | integer        | no       | X coordinate (for 'image' diff notes) |
+| `position[y]`             | integer        | no       | Y coordinate (for 'image' diff notes) |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions?body=comment
+```
+
+### Resolve a merge request discussion
+
+Resolve/unresolve whole discussion of a merge request.
+
+```
+PUT /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_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 |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `resolved`          | boolean        | yes      | Resolve/unresolve the discussion |
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7?resolved=true
+```
+
+
+### Add note to existing merge request discussion
+
+Adds a new note to the discussion.
+
+```
+POST /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_id/notes
+```
+
+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 |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `note_id`           | integer        | yes      | The ID of a discussion note |
+| `body`              | string         | yes      | The content of a discussion |
+| `created_at`        | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes?body=comment
+```
+
+### Modify an existing merge request discussion note
+
+Modify or resolve an existing discussion note of a merge request.
+
+```
+PUT /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_id/notes/:note_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 |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `note_id`           | integer        | yes      | The ID of a discussion note |
+| `body`              | string         | no       | The content of a discussion (exactly one of `body` or `resolved` must be set |
+| `resolved`          | boolean        | no       | Resolve/unresolve the note (exactly one of `body` or `resolved` must be set |
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes/1108?body=comment
+```
+
+Resolving a note:
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes/1108?resolved=true
+```
+
+### Delete a merge request discussion note
+
+Deletes an existing discussion note of a merge request.
+
+```
+DELETE /projects/:id/merge_requests/:merge_request_iid/discussions/:discussion_id/notes/:note_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 |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `note_id`           | integer        | yes      | The ID of a discussion note |
+
+```bash
+curl --request DELETE --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/discussions/636
+```
+
+## Commits
+
+### List project commit discussions
+
+Gets a list of all discussions for a single commit.
+
+```
+GET /projects/:id/commits/:commit_id/discussions
+```
+
+| Attribute           | Type             | Required   | Description  |
+| ------------------- | ---------------- | ---------- | ------------ |
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `commit_id`         | integer          | yes        | The ID of a commit |
+
+```json
+[
+  {
+    "id": "6a9c1750b37d513a43987b574953fceb50b03ce7",
+    "individual_note": false,
+    "notes": [
+      {
+        "id": 1126,
+        "type": "DiscussionNote",
+        "body": "discussion text",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-03T21:54:39.668Z",
+        "updated_at": "2018-03-03T21:54:39.668Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Commit",
+        "noteable_iid": null,
+        "resolvable": false
+      },
+      {
+        "id": 1129,
+        "type": "DiscussionNote",
+        "body": "reply to the discussion",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T13:38:02.127Z",
+        "updated_at": "2018-03-04T13:38:02.127Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Commit",
+        "noteable_iid": null,
+        "resolvable": false
+      }
+    ]
+  },
+  {
+    "id": "87805b7c09016a7058e91bdbe7b29d1f284a39e6",
+    "individual_note": true,
+    "notes": [
+      {
+        "id": 1128,
+        "type": null,
+        "body": "a single comment",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T09:17:22.520Z",
+        "updated_at": "2018-03-04T09:17:22.520Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Commit",
+        "noteable_iid": null,
+        "resolvable": false
+      }
+    ]
+  }
+]
+```
+
+Diff comments contain also position:
+
+```json
+[
+  {
+    "id": "87805b7c09016a7058e91bdbe7b29d1f284a39e6",
+    "individual_note": false,
+    "notes": [
+      {
+        "id": 1128,
+        "type": DiffNote,
+        "body": "diff comment",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T09:17:22.520Z",
+        "updated_at": "2018-03-04T09:17:22.520Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Commit",
+        "noteable_iid": null,
+        "position": {
+          "base_sha": "b5d6e7b1613fca24d250fa8e5bc7bcc3dd6002ef",
+          "start_sha": "7c9c2ead8a320fb7ba0b4e234bd9529a2614e306",
+          "head_sha": "4803c71e6b1833ca72b8b26ef2ecd5adc8a38031",
+          "old_path": "package.json",
+          "new_path": "package.json",
+          "position_type": "text",
+          "old_line": 27,
+          "new_line": 27
+        },
+        "resolvable": false
+      }
+    ]
+  }
+]
+```
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions
+```
+
+### Get single commit discussion
+
+Returns a single discussion for a specific project commit
+
+```
+GET /projects/:id/commits/:commit_id/discussions/:discussion_id
+```
+
+Parameters:
+
+| Attribute           | Type           | Required | Description |
+| ------------------- | -------------- | -------- | ----------- |
+| `id`                | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `commit_id`         | integer        | yes      | The ID of a commit |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7
+```
+
+### Create new commit discussion
+
+Creates a new discussion to a single project commit. This is similar to creating
+a note but but another comments (replies) can be added to it later.
+
+```
+POST /projects/:id/commits/:commit_id/discussions
+```
+
+Parameters:
+
+| Attribute                 | Type           | Required | Description |
+| ------------------------- | -------------- | -------- | ----------- |
+| `id`                      | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `commit_id`               | integer        | yes      | The ID of a commit |
+| `body`                    | string         | yes      | The content of a discussion |
+| `created_at`              | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+| `position`                | hash           | no       | Position when creating a diff note |
+| `position[base_sha]`      | string         | yes      | Base commit SHA in the source branch |
+| `position[start_sha]`     | string         | yes      | SHA referencing commit in target branch |
+| `position[head_sha]`      | string         | yes      | SHA referencing HEAD of this commit |
+| `position[position_type]` | string         | yes      | Type of the position reference', allowed values: 'text' or 'image' |
+| `position[new_path]`      | string         | no       | File path after change |
+| `position[new_line]`      | integer        | no       | Line number after change |
+| `position[old_path]`      | string         | no       | File path before change |
+| `position[old_line]`      | integer        | no       | Line number before change |
+| `position[width]`         | integer        | no       | Width of the image (for 'image' diff notes) |
+| `position[height]`        | integer        | no       | Height of the image (for 'image' diff notes) |
+| `position[x]`             | integer        | no       | X coordinate (for 'image' diff notes) |
+| `position[y]`             | integer        | no       | Y coordinate (for 'image' diff notes) |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions?body=comment
+```
+
+### Add note to existing commit discussion
+
+Adds a new note to the discussion.
+
+```
+POST /projects/:id/commits/:commit_id/discussions/:discussion_id/notes
+```
+
+Parameters:
+
+| Attribute           | Type           | Required | Description |
+| ------------------- | -------------- | -------- | ----------- |
+| `id`                | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `commit_id`         | integer        | yes      | The ID of a commit |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `note_id`           | integer        | yes      | The ID of a discussion note |
+| `body`              | string         | yes      | The content of a discussion |
+| `created_at`        | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes?body=comment
+```
+
+### Modify an existing commit discussion note
+
+Modify or resolve an existing discussion note of a commit.
+
+```
+PUT /projects/:id/commits/:commit_id/discussions/:discussion_id/notes/:note_id
+```
+
+Parameters:
+
+| Attribute           | Type           | Required | Description |
+| ------------------- | -------------- | -------- | ----------- |
+| `id`                | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `commit_id`         | integer        | yes      | The ID of a commit |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `note_id`           | integer        | yes      | The ID of a discussion note |
+| `body`              | string         | no       | The content of a note |
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes/1108?body=comment
+```
+
+Resolving a note:
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes/1108?resolved=true
+```
+
+### Delete a commit discussion note
+
+Deletes an existing discussion note of a commit.
+
+```
+DELETE /projects/:id/commits/:commit_id/discussions/:discussion_id/notes/:note_id
+```
+
+Parameters:
+
+| Attribute           | Type           | Required | Description |
+| ------------------- | -------------- | -------- | ----------- |
+| `id`                | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `commit_id`         | integer        | yes      | The ID of a commit |
+| `discussion_id`     | integer        | yes      | The ID of a discussion |
+| `note_id`           | integer        | yes      | The ID of a discussion note |
+
+```bash
+curl --request DELETE --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/commits/11/discussions/636
+```
diff --git a/doc/api/notes.md b/doc/api/notes.md
index aa38d22845c..d29c5b94915 100644
--- a/doc/api/notes.md
+++ b/doc/api/notes.md
@@ -39,7 +39,8 @@ GET /projects/:id/issues/:issue_iid/notes?sort=asc&order_by=updated_at
     "system": true,
     "noteable_id": 377,
     "noteable_type": "Issue",
-    "noteable_iid": 377
+    "noteable_iid": 377,
+    "resolvable": false
   },
   {
     "id": 305,
@@ -58,7 +59,8 @@ GET /projects/:id/issues/:issue_iid/notes?sort=asc&order_by=updated_at
     "system": true,
     "noteable_id": 121,
     "noteable_type": "Issue",
-    "noteable_iid": 121
+    "noteable_iid": 121,
+    "resolvable": false
   }
 ]
 ```
@@ -314,7 +316,8 @@ Parameters:
   "system": false,
   "noteable_id": 2,
   "noteable_type": "MergeRequest",
-  "noteable_iid": 2
+  "noteable_iid": 2,
+  "resolvable": false
 }
 ```
 
diff --git a/lib/api/discussions.rb b/lib/api/discussions.rb
index 7975f35ab1e..13c34e3473a 100644
--- a/lib/api/discussions.rb
+++ b/lib/api/discussions.rb
@@ -5,11 +5,12 @@ module API
 
     before { authenticate! }
 
-    NOTEABLE_TYPES = [Issue, Snippet].freeze
+    NOTEABLE_TYPES = [Issue, Snippet, MergeRequest, Commit].freeze
 
     NOTEABLE_TYPES.each do |noteable_type|
       parent_type = noteable_type.parent_class.to_s.underscore
       noteables_str = noteable_type.to_s.underscore.pluralize
+      noteables_path = noteable_type == Commit ? "repository/#{noteables_str}" : noteables_str
 
       params do
         requires :id, type: String, desc: "The ID of a #{parent_type}"
@@ -19,14 +20,12 @@ module API
           success Entities::Discussion
         end
         params do
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
           use :pagination
         end
-        get ":id/#{noteables_str}/:noteable_id/discussions" do
+        get ":id/#{noteables_path}/:noteable_id/discussions" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
 
-          break not_found!("Discussions") unless can?(current_user, noteable_read_ability_name(noteable), noteable)
-
           notes = noteable.notes
             .inc_relations_for_view
             .includes(:noteable)
@@ -43,13 +42,13 @@ module API
         end
         params do
           requires :discussion_id, type: String, desc: 'The ID of a discussion'
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
         end
-        get ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id" do
+        get ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
           notes = readable_discussion_notes(noteable, params[:discussion_id])
 
-          if notes.empty? || !can?(current_user, noteable_read_ability_name(noteable), noteable)
+          if notes.empty?
             break not_found!("Discussion")
           end
 
@@ -62,19 +61,36 @@ module API
           success Entities::Discussion
         end
         params do
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
           requires :body, type: String, desc: 'The content of a note'
           optional :created_at, type: String, desc: 'The creation date of the note'
+          optional :position, type: Hash do
+            requires :base_sha, type: String, desc: 'Base commit SHA in the source branch'
+            requires :start_sha, type: String, desc: 'SHA referencing commit in target branch'
+            requires :head_sha, type: String, desc: 'SHA referencing HEAD of this merge request'
+            requires :position_type, type: String, desc: 'Type of the position reference', values: %w(text image)
+            optional :new_path, type: String, desc: 'File path after change'
+            optional :new_line, type: Integer, desc: 'Line number after change'
+            optional :old_path, type: String, desc: 'File path before change'
+            optional :old_line, type: Integer, desc: 'Line number before change'
+            optional :width, type: Integer, desc: 'Width of the image'
+            optional :height, type: Integer, desc: 'Height of the image'
+            optional :x, type: Integer, desc: 'X coordinate in the image'
+            optional :y, type: Integer, desc: 'Y coordinate in the image'
+          end
         end
-        post ":id/#{noteables_str}/:noteable_id/discussions" do
+        post ":id/#{noteables_path}/:noteable_id/discussions" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+          type = params[:position] ? 'DiffNote' : 'DiscussionNote'
+          id_key = noteable.is_a?(Commit) ? :commit_id : :noteable_id
 
           opts = {
             note: params[:body],
             created_at: params[:created_at],
-            type: 'DiscussionNote',
+            type: type,
             noteable_type: noteables_str.classify,
-            noteable_id: noteable.id
+            position: params[:position],
+            id_key => noteable.id
           }
 
           note = create_note(noteable, opts)
@@ -91,13 +107,13 @@ module API
         end
         params do
           requires :discussion_id, type: String, desc: 'The ID of a discussion'
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
         end
-        get ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes" do
+        get ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id/notes" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
           notes = readable_discussion_notes(noteable, params[:discussion_id])
 
-          if notes.empty? || !can?(current_user, noteable_read_ability_name(noteable), noteable)
+          if notes.empty?
             break not_found!("Notes")
           end
 
@@ -108,12 +124,12 @@ module API
           success Entities::Note
         end
         params do
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
           requires :discussion_id, type: String, desc: 'The ID of a discussion'
           requires :body, type: String, desc: 'The content of a note'
           optional :created_at, type: String, desc: 'The creation date of the note'
         end
-        post ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes" do
+        post ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id/notes" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
           notes = readable_discussion_notes(noteable, params[:discussion_id])
 
@@ -139,11 +155,11 @@ module API
           success Entities::Note
         end
         params do
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
           requires :discussion_id, type: String, desc: 'The ID of a discussion'
           requires :note_id, type: Integer, desc: 'The ID of a note'
         end
-        get ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+        get ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
 
           get_note(noteable, params[:note_id])
@@ -153,30 +169,52 @@ module API
           success Entities::Note
         end
         params do
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
           requires :discussion_id, type: String, desc: 'The ID of a discussion'
           requires :note_id, type: Integer, desc: 'The ID of a note'
-          requires :body, type: String, desc: 'The content of a note'
+          optional :body, type: String, desc: 'The content of a note'
+          optional :resolved, type: Boolean, desc: 'Mark note resolved/unresolved'
+          exactly_one_of :body, :resolved
         end
-        put ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+        put ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
 
-          update_note(noteable, params[:note_id])
+          if params[:resolved].nil?
+            update_note(noteable, params[:note_id])
+          else
+            resolve_note(noteable, params[:note_id], params[:resolved])
+          end
         end
 
         desc "Delete a comment in a #{noteable_type.to_s.downcase} discussion" do
           success Entities::Note
         end
         params do
-          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
           requires :discussion_id, type: String, desc: 'The ID of a discussion'
           requires :note_id, type: Integer, desc: 'The ID of a note'
         end
-        delete ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+        delete ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
 
           delete_note(noteable, params[:note_id])
         end
+
+        if Noteable::RESOLVABLE_TYPES.include?(noteable_type.to_s)
+          desc "Resolve/unresolve an existing #{noteable_type.to_s.downcase} discussion" do
+            success Entities::Discussion
+          end
+          params do
+            requires :noteable_id, types: [Integer, String], desc: 'The ID of the noteable'
+            requires :discussion_id, type: String, desc: 'The ID of a discussion'
+            requires :resolved, type: Boolean, desc: 'Mark discussion resolved/unresolved'
+          end
+          put ":id/#{noteables_path}/:noteable_id/discussions/:discussion_id" do
+            noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+
+            resolve_discussion(noteable, params[:discussion_id], params[:resolved])
+          end
+        end
       end
     end
 
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 8aad320e376..75d56b82424 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -286,6 +286,10 @@ module API
       end
     end
 
+    class DiffRefs < Grape::Entity
+      expose :base_sha, :head_sha, :start_sha
+    end
+
     class Commit < Grape::Entity
       expose :id, :short_id, :title, :created_at
       expose :parent_ids
@@ -601,6 +605,8 @@ module API
         merge_request.metrics&.pipeline
       end
 
+      expose :diff_refs, using: Entities::DiffRefs
+
       def build_available?(options)
         options[:project]&.feature_available?(:builds, options[:current_user])
       end
@@ -642,6 +648,11 @@ module API
       expose :id, :key, :created_at
     end
 
+    class DiffPosition < Grape::Entity
+      expose :base_sha, :start_sha, :head_sha, :old_path, :new_path,
+        :position_type
+    end
+
     class Note < Grape::Entity
       # Only Issue and MergeRequest have iid
       NOTEABLE_TYPES_WITH_IID = %w(Issue MergeRequest).freeze
@@ -655,6 +666,14 @@ module API
       expose :system?, as: :system
       expose :noteable_id, :noteable_type
 
+      expose :position, if: ->(note, options) { note.diff_note? } do |note|
+        note.position.to_h
+      end
+
+      expose :resolvable?, as: :resolvable
+      expose :resolved?, as: :resolved, if: ->(note, options) { note.resolvable? }
+      expose :resolved_by, using: Entities::UserBasic, if: ->(note, options) { note.resolvable? }
+
       # Avoid N+1 queries as much as possible
       expose(:noteable_iid) { |note| note.noteable.iid if NOTEABLE_TYPES_WITH_IID.include?(note.noteable_type) }
     end
diff --git a/lib/api/helpers.rb b/lib/api/helpers.rb
index b8657cd7ee4..2ed331d4fd2 100644
--- a/lib/api/helpers.rb
+++ b/lib/api/helpers.rb
@@ -171,6 +171,10 @@ module API
       MergeRequestsFinder.new(current_user, project_id: user_project.id).find_by!(iid: iid)
     end
 
+    def find_project_commit(id)
+      user_project.commit_by(oid: id)
+    end
+
     def find_project_snippet(id)
       finder_params = { project: user_project }
       SnippetsFinder.new(current_user, finder_params).find(id)
diff --git a/lib/api/helpers/notes_helpers.rb b/lib/api/helpers/notes_helpers.rb
index b74b8149834..b4bfb677d72 100644
--- a/lib/api/helpers/notes_helpers.rb
+++ b/lib/api/helpers/notes_helpers.rb
@@ -21,6 +21,23 @@ module API
         end
       end
 
+      def resolve_note(noteable, note_id, resolved)
+        note = noteable.notes.find(note_id)
+
+        authorize! :resolve_note, note
+
+        bad_request!("Note is not resolvable") unless note.resolvable?
+
+        if resolved
+          parent = noteable_parent(noteable)
+          ::Notes::ResolveService.new(parent, current_user).execute(note)
+        else
+          note.unresolve!
+        end
+
+        present note, with: Entities::Note
+      end
+
       def delete_note(noteable, note_id)
         note = noteable.notes.find(note_id)
 
@@ -35,7 +52,7 @@ module API
 
       def get_note(noteable, note_id)
         note = noteable.notes.with_metadata.find(params[:note_id])
-        can_read_note = can?(current_user, noteable_read_ability_name(noteable), noteable) && !note.cross_reference_not_visible_for?(current_user)
+        can_read_note = !note.cross_reference_not_visible_for?(current_user)
 
         if can_read_note
           present note, with: Entities::Note
@@ -49,7 +66,20 @@ module API
       end
 
       def find_noteable(parent, noteables_str, noteable_id)
-        public_send("find_#{parent}_#{noteables_str.singularize}", noteable_id) # rubocop:disable GitlabSecurity/PublicSend
+        noteable = public_send("find_#{parent}_#{noteables_str.singularize}", noteable_id) # rubocop:disable GitlabSecurity/PublicSend
+
+        readable =
+          if noteable.is_a?(Commit)
+            # for commits there is not :read_commit policy, check if user
+            # has :read_note permission on the commit's project
+            can?(current_user, :read_note, user_project)
+          else
+            can?(current_user, noteable_read_ability_name(noteable), noteable)
+          end
+
+        return not_found!(noteables_str) unless readable
+
+        noteable
       end
 
       def noteable_parent(noteable)
@@ -57,11 +87,8 @@ module API
       end
 
       def create_note(noteable, opts)
-        noteables_str = noteable.model_name.to_s.underscore.pluralize
-
-        return not_found!(noteables_str) unless can?(current_user, noteable_read_ability_name(noteable), noteable)
-
-        authorize! :create_note, noteable
+        policy_object = noteable.is_a?(Commit) ? user_project : noteable
+        authorize!(:create_note, policy_object)
 
         parent = noteable_parent(noteable)
 
@@ -73,6 +100,21 @@ module API
         project = parent if parent.is_a?(Project)
         ::Notes::CreateService.new(project, current_user, opts).execute
       end
+
+      def resolve_discussion(noteable, discussion_id, resolved)
+        discussion = noteable.find_discussion(discussion_id)
+
+        forbidden! unless discussion.can_resolve?(current_user)
+
+        if resolved
+          parent = noteable_parent(noteable)
+          ::Discussions::ResolveService.new(parent, current_user, merge_request: noteable).execute(discussion)
+        else
+          discussion.unresolve!
+        end
+
+        present discussion, with: Entities::Discussion
+      end
     end
   end
 end
diff --git a/lib/api/notes.rb b/lib/api/notes.rb
index 69f1df6b341..39923e6d5b5 100644
--- a/lib/api/notes.rb
+++ b/lib/api/notes.rb
@@ -31,23 +31,19 @@ module API
         get ":id/#{noteables_str}/:noteable_id/notes" do
           noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
 
-          if can?(current_user, noteable_read_ability_name(noteable), noteable)
-            # We exclude notes that are cross-references and that cannot be viewed
-            # by the current user. By doing this exclusion at this level and not
-            # at the DB query level (which we cannot in that case), the current
-            # page can have less elements than :per_page even if
-            # there's more than one page.
-            raw_notes = noteable.notes.with_metadata.reorder(params[:order_by] => params[:sort])
-            notes =
-              # paginate() only works with a relation. This could lead to a
-              # mismatch between the pagination headers info and the actual notes
-              # array returned, but this is really a edge-case.
-              paginate(raw_notes)
-              .reject { |n| n.cross_reference_not_visible_for?(current_user) }
-            present notes, with: Entities::Note
-          else
-            not_found!("Notes")
-          end
+          # We exclude notes that are cross-references and that cannot be viewed
+          # by the current user. By doing this exclusion at this level and not
+          # at the DB query level (which we cannot in that case), the current
+          # page can have less elements than :per_page even if
+          # there's more than one page.
+          raw_notes = noteable.notes.with_metadata.reorder(params[:order_by] => params[:sort])
+          notes =
+            # paginate() only works with a relation. This could lead to a
+            # mismatch between the pagination headers info and the actual notes
+            # array returned, but this is really a edge-case.
+            paginate(raw_notes)
+            .reject { |n| n.cross_reference_not_visible_for?(current_user) }
+          present notes, with: Entities::Note
         end
 
         desc "Get a single #{noteable_type.to_s.downcase} note" do
diff --git a/lib/gitlab/diff/position.rb b/lib/gitlab/diff/position.rb
index 690b27cde81..978962ab2eb 100644
--- a/lib/gitlab/diff/position.rb
+++ b/lib/gitlab/diff/position.rb
@@ -12,6 +12,10 @@ module Gitlab
                :head_sha,
                :old_line,
                :new_line,
+               :width,
+               :height,
+               :x,
+               :y,
                :position_type, to: :formatter
 
       # A position can belong to a text line or to an image coordinate
diff --git a/spec/fixtures/api/schemas/public_api/v4/notes.json b/spec/fixtures/api/schemas/public_api/v4/notes.json
index 4c4ca3b582f..0f9c221fd6d 100644
--- a/spec/fixtures/api/schemas/public_api/v4/notes.json
+++ b/spec/fixtures/api/schemas/public_api/v4/notes.json
@@ -24,7 +24,10 @@
       "system": { "type": "boolean" },
       "noteable_id": { "type": "integer" },
       "noteable_iid": { "type": "integer" },
-      "noteable_type": { "type": "string" }
+      "noteable_type": { "type": "string" },
+      "resolved": { "type": "boolean" },
+      "resolvable": { "type": "boolean" },
+      "resolved_by": { "type": ["string", "null"] }
     },
     "required": [
       "id", "body", "attachment", "author", "created_at", "updated_at",
diff --git a/spec/requests/api/discussions_spec.rb b/spec/requests/api/discussions_spec.rb
index 4a44b219a67..ef34192f888 100644
--- a/spec/requests/api/discussions_spec.rb
+++ b/spec/requests/api/discussions_spec.rb
@@ -2,32 +2,53 @@ require 'spec_helper'
 
 describe API::Discussions do
   let(:user) { create(:user) }
-  let!(:project) { create(:project, :public, namespace: user.namespace) }
+  let!(:project) { create(:project, :public, :repository, namespace: user.namespace) }
   let(:private_user)    { create(:user) }
 
   before do
-    project.add_reporter(user)
+    project.add_developer(user)
   end
 
-  context "when noteable is an Issue" do
+  context 'when noteable is an Issue' do
     let!(:issue) { create(:issue, project: project, author: user) }
     let!(:issue_note) { create(:discussion_note_on_issue, noteable: issue, project: project, author: user) }
 
-    it_behaves_like "discussions API", 'projects', 'issues', 'iid' do
+    it_behaves_like 'discussions API', 'projects', 'issues', 'iid' do
       let(:parent) { project }
       let(:noteable) { issue }
       let(:note) { issue_note }
     end
   end
 
-  context "when noteable is a Snippet" do
+  context 'when noteable is a Snippet' do
     let!(:snippet) { create(:project_snippet, project: project, author: user) }
     let!(:snippet_note) { create(:discussion_note_on_snippet, noteable: snippet, project: project, author: user) }
 
-    it_behaves_like "discussions API", 'projects', 'snippets', 'id' do
+    it_behaves_like 'discussions API', 'projects', 'snippets', 'id' do
       let(:parent) { project }
       let(:noteable) { snippet }
       let(:note) { snippet_note }
     end
   end
+
+  context 'when noteable is a Merge Request' do
+    let!(:noteable) { create(:merge_request_with_diffs, source_project: project, target_project: project, author: user) }
+    let!(:note) { create(:discussion_note_on_merge_request, noteable: noteable, project: project, author: user) }
+    let!(:diff_note) { create(:diff_note_on_merge_request, noteable: noteable, project: project, author: user) }
+    let(:parent) { project }
+
+    it_behaves_like 'discussions API', 'projects', 'merge_requests', 'iid'
+    it_behaves_like 'diff discussions API', 'projects', 'merge_requests', 'iid'
+    it_behaves_like 'resolvable discussions API', 'projects', 'merge_requests', 'iid'
+  end
+
+  context 'when noteable is a Commit' do
+    let!(:noteable) { create(:commit, project: project, author: user) }
+    let!(:note) { create(:discussion_note_on_commit, commit_id: noteable.id, project: project, author: user) }
+    let!(:diff_note) { create(:diff_note_on_commit, commit_id: noteable.id, project: project, author: user) }
+    let(:parent) { project }
+
+    it_behaves_like 'discussions API', 'projects', 'repository/commits', 'id'
+    it_behaves_like 'diff discussions API', 'projects', 'repository/commits', 'id'
+  end
 end
diff --git a/spec/services/notes/resolve_service_spec.rb b/spec/services/notes/resolve_service_spec.rb
new file mode 100644
index 00000000000..b54d40a7a5c
--- /dev/null
+++ b/spec/services/notes/resolve_service_spec.rb
@@ -0,0 +1,23 @@
+require 'spec_helper'
+
+describe Notes::ResolveService do
+  let(:merge_request) { create(:merge_request) }
+  let(:note) { create(:diff_note_on_merge_request, noteable: merge_request, project: merge_request.project) }
+  let(:user) { merge_request.author }
+
+  describe '#execute' do
+    it "resolves the note" do
+      described_class.new(merge_request.project, user).execute(note)
+      note.reload
+
+      expect(note.resolved?).to be true
+      expect(note.resolved_by).to eq(user)
+    end
+
+    it "sends notifications if all discussions are resolved" do
+      expect_any_instance_of(MergeRequests::ResolvedDiscussionNotificationService).to receive(:execute).with(merge_request)
+
+      described_class.new(merge_request.project, user).execute(note)
+    end
+  end
+end
diff --git a/spec/support/shared_examples/requests/api/diff_discussions.rb b/spec/support/shared_examples/requests/api/diff_discussions.rb
new file mode 100644
index 00000000000..85a4bd8ca27
--- /dev/null
+++ b/spec/support/shared_examples/requests/api/diff_discussions.rb
@@ -0,0 +1,57 @@
+shared_examples 'diff discussions API' do |parent_type, noteable_type, id_name|
+  describe "GET /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions" do
+    it "includes diff discussions" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user)
+
+      discussion = json_response.find { |record| record['id'] == diff_note.discussion_id }
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(discussion).not_to be_nil
+      expect(discussion['individual_note']).to eq(false)
+      expect(discussion['notes'].first['body']).to eq(diff_note.note)
+    end
+  end
+
+  describe "GET /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id" do
+    it "returns a discussion by id" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions/#{diff_note.discussion_id}", user)
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['id']).to eq(diff_note.discussion_id)
+      expect(json_response['notes'].first['body']).to eq(diff_note.note)
+      expect(json_response['notes'].first['position']).to eq(diff_note.position.to_h.stringify_keys)
+    end
+  end
+
+  describe "POST /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions" do
+    it "creates a new diff note" do
+      position = diff_note.position.to_h
+
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user), body: 'hi!', position: position
+
+      expect(response).to have_gitlab_http_status(201)
+      expect(json_response['notes'].first['body']).to eq('hi!')
+      expect(json_response['notes'].first['type']).to eq('DiffNote')
+      expect(json_response['notes'].first['position']).to eq(position.stringify_keys)
+    end
+
+    it "returns a 400 bad request error when position is invalid" do
+      position = diff_note.position.to_h.merge(new_line: '100000')
+
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user), body: 'hi!', position: position
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+  end
+
+  describe "POST /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id/notes" do
+    it 'adds a new note to the diff discussion' do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+               "discussions/#{diff_note.discussion_id}/notes", user), body: 'hi!'
+
+      expect(response).to have_gitlab_http_status(201)
+      expect(json_response['body']).to eq('hi!')
+      expect(json_response['type']).to eq('DiffNote')
+    end
+  end
+end
diff --git a/spec/support/shared_examples/requests/api/resolvable_discussions.rb b/spec/support/shared_examples/requests/api/resolvable_discussions.rb
new file mode 100644
index 00000000000..408ad08cc48
--- /dev/null
+++ b/spec/support/shared_examples/requests/api/resolvable_discussions.rb
@@ -0,0 +1,87 @@
+shared_examples 'resolvable discussions API' do |parent_type, noteable_type, id_name|
+  describe "PUT /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id" do
+    it "resolves discussion if resolved is true" do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}", user), resolved: true
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['notes'].size).to eq(1)
+      expect(json_response['notes'][0]['resolved']).to eq(true)
+    end
+
+    it "unresolves discussion if resolved is false" do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}", user), resolved: false
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['notes'].size).to eq(1)
+      expect(json_response['notes'][0]['resolved']).to eq(false)
+    end
+
+    it "returns a 400 bad request error if resolved parameter is not passed" do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+
+    it "returns a 401 unauthorized error if user is not authenticated" do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}"), resolved: true
+
+      expect(response).to have_gitlab_http_status(401)
+    end
+
+    it "returns a 403 error if user resolves discussion of someone else" do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}", private_user), resolved: true
+
+      expect(response).to have_gitlab_http_status(403)
+    end
+
+    context 'when user does not have access to read the discussion' do
+      before do
+        parent.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+      end
+
+      it 'responds with 404' do
+        put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                "discussions/#{note.discussion_id}", private_user), resolved: true
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+  end
+
+  describe "PUT /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+    it 'returns resolved note when resolved parameter is true' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/#{note.id}", user), resolved: true
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['resolved']).to eq(true)
+    end
+
+    it 'returns a 404 error when note id not found' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/12345", user),
+              body: 'Hello!'
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it 'returns a 400 bad request error if neither body nor resolved parameter is given' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/#{note.id}", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+
+    it "returns a 403 error if user resolves note of someone else" do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/#{note.id}", private_user), resolved: true
+
+      expect(response).to have_gitlab_http_status(403)
+    end
+  end
+end