feat(platform/gitlab): handle detailed_merge_status to proceed with automerge

docs/usage/self-hosted-experimental.md

@@ -96,7 +96,7 @@ If set, Renovate will terminate the whole process group of a terminated child pr
 ## `RENOVATE_X_GITLAB_AUTO_MERGEABLE_CHECK_ATTEMPS`
 
 If set to an positive integer, Renovate will use this as the number of attempts to check if a merge request on GitLab is mergable before trying to automerge.
-The formula for the delay between attempts is `250 * attempt * attempt` milliseconds.
+The formula for the delay between attempts is `RENOVATE_X_GITLAB_MERGE_REQUEST_DELAY * attempt * attempt` milliseconds.
 
 Default value: `5` (attempts results in max. 13.75 seconds timeout).
 
@@ -108,6 +108,12 @@ Can be useful for slow-running, self-hosted GitLab instances that don't react fa
 
 Default value: `1000` (milliseconds).
 
+## `RENOVATE_X_GITLAB_MERGE_REQUEST_DELAY`
+
+If set, Renovate will use this as a delay to proceed with an automerge.
+
+Default value: `250` (milliseconds).
+
 ## `RENOVATE_X_HARD_EXIT`
 
 If set to any value, Renovate will use a "hard" `process.exit()` once all work is done, even if a sub-process is otherwise delaying Node.js from exiting.

lib/modules/platform/gitlab/index.spec.ts

@@ -1824,6 +1824,49 @@ describe('modules/platform/gitlab/index', () => {
       ]);
     });
 
+    it('should parse detailed_merge_status attribute on >= 15.6', async () => {
+      await initPlatform('15.6.0-ee');
+      httpMock
+        .scope(gitlabApiHost)
+        .post('/api/v4/projects/undefined/merge_requests')
+        .reply(200, {
+          id: 1,
+          iid: 12345,
+          title: 'some title',
+        })
+        .get('/api/v4/projects/undefined/merge_requests/12345')
+        .reply(200)
+        .get('/api/v4/projects/undefined/merge_requests/12345')
+        .reply(200)
+        .get('/api/v4/projects/undefined/merge_requests/12345')
+        .reply(200)
+        .put('/api/v4/projects/undefined/merge_requests/12345/merge')
+        .reply(200);
+      process.env.RENOVATE_X_GITLAB_AUTO_MERGEABLE_CHECK_ATTEMPS = '3';
+      process.env.RENOVATE_X_GITLAB_MERGE_REQUEST_DELAY = '250';
+      const pr = await gitlab.createPr({
+        sourceBranch: 'some-branch',
+        targetBranch: 'master',
+        prTitle: 'some-title',
+        prBody: 'the-body',
+        platformOptions: {
+          usePlatformAutomerge: true,
+        },
+      });
+      expect(pr).toEqual({
+        id: 1,
+        iid: 12345,
+        number: 12345,
+        sourceBranch: 'some-branch',
+        title: 'some title',
+      });
+      expect(timers.setTimeout.mock.calls).toMatchObject([
+        [250],
+        [1000],
+        [2250],
+      ]);
+    });
+
     it('raises with squash enabled when repository squash option is default_on', async () => {
       await initPlatform('14.0.0');
 

lib/modules/platform/gitlab/index.ts

@@ -644,26 +644,46 @@ async function tryPrAutomerge(
         await ignoreApprovals(pr);
       }
 
-      const desiredStatus = 'can_be_merged';
+      let desiredStatus = 'can_be_merged';
       // The default value of 5 attempts results in max. 13.75 seconds timeout if no pipeline created.
       const retryTimes = parseInteger(
         process.env.RENOVATE_X_GITLAB_AUTO_MERGEABLE_CHECK_ATTEMPS,
         5,
       );
 
+      if (semver.gte(defaults.version, '15.6.0')) {
+        logger.trace(
+          { version: defaults.version },
+          'In GitLab 15.6 merge_status, using detailed_merge_status to check the merge request status',
+        );
+        desiredStatus = 'mergeable';
+      }
+
+      const mergeDelay = parseInteger(
+        process.env.RENOVATE_X_GITLAB_MERGE_REQUEST_DELAY,
+        250,
+      );
+
       // Check for correct merge request status before setting `merge_when_pipeline_succeeds` to  `true`.
       for (let attempt = 1; attempt <= retryTimes; attempt += 1) {
         const { body } = await gitlabApi.getJson<{
           merge_status: string;
+          detailed_merge_status?: string;
           pipeline: string;
         }>(`projects/${config.repository}/merge_requests/${pr}`, {
           memCache: false,
         });
         // Only continue if the merge request can be merged and has a pipeline.
-        if (body.merge_status === desiredStatus && body.pipeline !== null) {
+        if (
+          ((desiredStatus === 'mergeable' &&
+            body.detailed_merge_status === desiredStatus) ||
+            (desiredStatus === 'can_be_merged' &&
+              body.merge_status === desiredStatus)) &&
+          body.pipeline !== null
+        ) {
           break;
         }
-        await setTimeout(250 * attempt ** 2); // exponential backoff
+        await setTimeout(mergeDelay * attempt ** 2); // exponential backoff
       }
 
       await gitlabApi.putJson(