Add MR squashing to API

doc/api/merge_requests.md

@@ -75,6 +75,7 @@ Parameters:
     "approvals_before_merge": null
     "should_remove_source_branch": true,
     "force_remove_source_branch": false,
+    "squash": false,
     "web_url": "http://example.com/example/example/merge_requests/1"
   }
 ]
@@ -145,6 +146,7 @@ Parameters:
   "approvals_before_merge": null
   "should_remove_source_branch": true,
   "force_remove_source_branch": false,
+  "squash": false,
   "web_url": "http://example.com/example/example/merge_requests/1"
 }
 ```
@@ -251,6 +253,7 @@ Parameters:
   "approvals_before_merge": null,
   "should_remove_source_branch": true,
   "force_remove_source_branch": false,
+  "squash": false,
   "web_url": "http://example.com/example/example/merge_requests/1",
   "changes": [
     {
@@ -287,6 +290,7 @@ POST /projects/:id/merge_requests
 | `milestone_id` | integer  | no | The ID of a milestone |
 | `remove_source_branch` | boolean  | no | Flag indicating if a merge request should remove the source branch when merging |
 | `approvals_before_merge` | integer| no | Number of approvals required before this can be merged (see below) |
+| `squash` | boolean| no | Squash commits into a single commit when merging |
 
 If `approvals_before_merge` is not provided, it inherits the value from the
 target project. If it is provided, then the following conditions must hold in
@@ -349,6 +353,7 @@ order for it to take effect:
   "approvals_before_merge": null
   "should_remove_source_branch": true,
   "force_remove_source_branch": false,
+  "squash": false,
   "web_url": "http://example.com/example/example/merge_requests/1"
 }
 ```
@@ -374,6 +379,7 @@ PUT /projects/:id/merge_requests/:merge_request_id
 | `labels` | string  | no | Labels for MR as a comma-separated list |
 | `milestone_id` | integer  | no | The ID of a milestone |
 | `remove_source_branch` | boolean  | no | Flag indicating if a merge request should remove the source branch when merging |
+| `squash` | boolean| no | Squash commits into a single commit when merging |
 
 ```json
 {
@@ -426,6 +432,7 @@ PUT /projects/:id/merge_requests/:merge_request_id
   "approvals_before_merge": null
   "should_remove_source_branch": true,
   "force_remove_source_branch": false,
+  "squash": false,
   "web_url": "http://example.com/example/example/merge_requests/1"
 }
 ```
@@ -471,7 +478,19 @@ Parameters:
 - `merge_commit_message` (optional)         - Custom merge commit message
 - `should_remove_source_branch` (optional)  - if `true` removes the source branch
 - `merge_when_build_succeeds` (optional)    - if `true` the MR is merged when the build succeeds
-- `sha` (optional)                          - if present, then this SHA must match the HEAD of the source branch, otherwise the merge will fail
+- `sha` (optional)                          - if present, then this SHA must
+
+
+| Attribute | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `id` | string | yes | The ID of a project |
+| `merge_request_id` | integer | yes | The ID of the merge request |
+| `merge_commit_message` | string | no | Custom merge commit message |
+| `should_remove_source_branch` | boolean | no | Remove the source branch after merge |
+| `merge_when_build_succeeds` | boolean | no | Merge when build succeeds, rather than immediately |
+| `sha` | string | no  | If present, then this SHA must match the HEAD of the source branch, otherwise the merge will fail |
+| `squash` | boolean | no | Squash the merge request into a single commit |
+
 
 ```json
 {
@@ -525,6 +544,7 @@ Parameters:
   "approvals_before_merge": null
   "should_remove_source_branch": true,
   "force_remove_source_branch": false,
+  "squash": false,
   "web_url": "http://example.com/example/example/merge_requests/1"
 }
 ```
@@ -698,6 +718,7 @@ Parameters:
   "approvals_before_merge": null
   "should_remove_source_branch": true,
   "force_remove_source_branch": false,
+  "squash": false,
   "web_url": "http://example.com/example/example/merge_requests/1"
 }
 ```
@@ -1021,6 +1042,7 @@ Example response:
     "user_notes_count": 7,
     "should_remove_source_branch": true,
     "force_remove_source_branch": false,
+    "squash": true,
     "web_url": "http://example.com/example/example/merge_requests/1"
   },
   "target_url": "https://gitlab.example.com/gitlab-org/gitlab-ci/merge_requests/7",

lib/api/entities.rb

@@ -326,6 +326,7 @@ module API
       expose :approvals_before_merge
       expose :should_remove_source_branch?, as: :should_remove_source_branch
       expose :force_remove_source_branch?, as: :force_remove_source_branch
+      expose :squash
 
       expose :web_url do |merge_request, options|
         Gitlab::UrlBuilder.build(merge_request)

lib/api/merge_requests.rb

@@ -34,6 +34,7 @@ module API
           optional :labels, type: String, desc: 'Comma-separated list of label names'
           optional :approvals_before_merge, type: Integer, desc: 'Number of approvals required before this can be merged'
           optional :remove_source_branch, type: Boolean, desc: 'Remove source branch when merging'
+          optional :squash, type: Boolean, desc: 'Squash commits when merging'
         end
       end
 
@@ -153,7 +154,7 @@ module API
           use :optional_params
           at_least_one_of :title, :target_branch, :description, :assignee_id,
                           :milestone_id, :labels, :state_event, :approvals_before_merge,
-                          :remove_source_branch
+                          :remove_source_branch, :squash
         end
         put path do
           merge_request = find_merge_request_with_access(params.delete(:merge_request_id), :update_merge_request)
@@ -180,6 +181,7 @@ module API
           optional :merge_when_build_succeeds, type: Boolean,
                                                desc: 'When true, this merge request will be merged when the pipeline succeeds'
           optional :sha, type: String, desc: 'When present, must have the HEAD SHA of the source branch'
+          optional :squash, type: Boolean, desc: 'When true, the commits will be squashed into a single commit on merge'
         end
         put "#{path}/merge" do
           merge_request = find_project_merge_request(params[:merge_request_id])
@@ -196,6 +198,10 @@ module API
             render_api_error!("SHA does not match HEAD of source branch: #{merge_request.diff_head_sha}", 409)
           end
 
+          if params[:squash]
+            merge_request.update(squash: params[:squash])
+          end
+
           merge_params = {
             commit_message: params[:merge_commit_message],
             should_remove_source_branch: params[:should_remove_source_branch]

spec/requests/api/merge_requests_spec.rb

@@ -39,6 +39,7 @@ describe API::MergeRequests, api: true  do
         expect(json_response.first['sha']).to eq(merge_request_merged.diff_head_sha)
         expect(json_response.first['merge_commit_sha']).not_to be_nil
         expect(json_response.first['merge_commit_sha']).to eq(merge_request_merged.merge_commit_sha)
+        expect(json_response.first['squash']).to eq(merge_request_merged.squash)
       end
 
       it "returns an array of all merge_requests" do
@@ -233,13 +234,15 @@ describe API::MergeRequests, api: true  do
              author: user,
              labels: 'label, label2',
              milestone_id: milestone.id,
-             remove_source_branch: true
+             remove_source_branch: true,
+             squash: true
 
         expect(response).to have_http_status(201)
         expect(json_response['title']).to eq('Test merge_request')
         expect(json_response['labels']).to eq(['label', 'label2'])
         expect(json_response['milestone']['id']).to eq(milestone.id)
         expect(json_response['force_remove_source_branch']).to be_truthy
+        expect(json_response['squash']).to be_truthy
       end
 
       it "returns 422 when source_branch equals target_branch" do
@@ -526,6 +529,14 @@ describe API::MergeRequests, api: true  do
       expect(response).to have_http_status(200)
     end
 
+    it "updates the MR's squash attribute" do
+      expect do
+        put api("/projects/#{project.id}/merge_requests/#{merge_request.id}/merge", user), squash: true
+      end.to change { merge_request.reload.squash }
+
+      expect(response).to have_http_status(200)
+    end
+
     it "enables merge when pipeline succeeds if the pipeline is active" do
       allow_any_instance_of(MergeRequest).to receive(:head_pipeline).and_return(pipeline)
       allow(pipeline).to receive(:active?).and_return(true)
@@ -566,6 +577,13 @@ describe API::MergeRequests, api: true  do
       expect(json_response['milestone']['id']).to eq(milestone.id)
     end
 
+    it "updates squash and returns merge_request" do
+      put api("/projects/#{project.id}/merge_requests/#{merge_request.id}", user), squash: true
+
+      expect(response).to have_http_status(200)
+      expect(json_response['squash']).to be_truthy
+    end
+
     it "returns merge_request with renamed target_branch" do
       put api("/projects/#{project.id}/merge_requests/#{merge_request.id}", user), target_branch: "wiki"
       expect(response).to have_http_status(200)