feat(config/presets): fetchJSONFile handle branchOrTag in Bitbucket Server (#13005)

Co-authored-by: Michael Kriese <michael.kriese@visualon.de>

lib/config/presets/bitbucket-server/__snapshots__/index.spec.ts.snap

 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`config/presets/bitbucket-server/index fetchJSONFile() handles branches/tags 1`] = `
+Array [
+  Object {
+    "headers": Object {
+      "accept": "application/json",
+      "accept-encoding": "gzip, deflate, br",
+      "authorization": "Bearer abc",
+      "host": "git.company.org",
+      "user-agent": "RenovateBot/0.0.0-semantic-release (https://github.com/renovatebot/renovate)",
+      "x-atlassian-token": "no-check",
+    },
+    "method": "GET",
+    "url": "https://git.company.org/rest/api/1.0/projects/some/repos/repo/browse/some-filename.json?limit=20000&at=feature%2Fbranch",
+  },
+]
+`;
+
 exports[`config/presets/bitbucket-server/index fetchJSONFile() returns JSON 1`] = `
 Array [
   Object {

lib/config/presets/bitbucket-server/index.spec.ts

@@ -36,6 +36,26 @@ describe('config/presets/bitbucket-server/index', () => {
       expect(httpMock.getTrace()).toMatchSnapshot();
     });
 
+    it('handles branches/tags', async () => {
+      httpMock
+        .scope(bitbucketApiHost)
+        .get(`${basePath}/some-filename.json`)
+        .query({ limit: 20000, at: 'feature/branch' })
+        .reply(200, {
+          isLastPage: true,
+          lines: [{ text: '{"from":"api"' }, { text: '}' }],
+        });
+
+      const res = await bitbucketServer.fetchJSONFile(
+        'some/repo',
+        'some-filename.json',
+        bitbucketApiHost,
+        'feature/branch'
+      );
+      expect(res).toEqual({ from: 'api' });
+      expect(httpMock.getTrace()).toMatchSnapshot();
+    });
+
     it('throws 404', async () => {
       httpMock
         .scope(bitbucketApiHost)

lib/config/presets/bitbucket-server/index.ts

@@ -17,11 +17,16 @@ const http = new BitbucketServerHttp();
 export async function fetchJSONFile(
   repo: string,
   fileName: string,
-  endpoint: string
+  endpoint: string,
+  branchOrTag?: string
 ): Promise<Preset> {
   const [projectKey, repositorySlug] = repo.split('/');
   setBaseUrl(endpoint);
-  const url = `rest/api/1.0/projects/${projectKey}/repos/${repositorySlug}/browse/${fileName}?limit=20000`;
+  let url = `rest/api/1.0/projects/${projectKey}/repos/${repositorySlug}/browse/${fileName}?limit=20000`;
+  if (branchOrTag) {
+    url += '&at=' + encodeURIComponent(branchOrTag);
+  }
+
   let res: { body: FileData };
   try {
     res = await http.getJson(url);