fix(github): try push branch if rebase fails

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

@@ -3332,5 +3332,63 @@ describe('modules/platform/github/index', () => {
 
       expect(res).toBe('0abcdef');
     });
+
+    it('continues if rebase fails due to 422', async () => {
+      git.pushCommitToRenovateRef.mockResolvedValueOnce();
+      git.listCommitTree.mockResolvedValueOnce([]);
+
+      const scope = httpMock.scope(githubApiHost);
+
+      initRepoMock(scope, 'some/repo');
+      await github.initRepo({ repository: 'some/repo' });
+
+      scope
+        .post('/repos/some/repo/git/trees')
+        .reply(200, { sha: '111' })
+        .post('/repos/some/repo/git/commits')
+        .reply(200, { sha: '222' })
+        .head('/repos/some/repo/git/refs/heads/foo/bar')
+        .reply(200)
+        .patch('/repos/some/repo/git/refs/heads/foo/bar')
+        .reply(422)
+        .post('/repos/some/repo/git/refs')
+        .reply(200);
+
+      const res = await github.commitFiles({
+        branchName: 'foo/bar',
+        files: [{ type: 'addition', path: 'foo.bar', contents: 'foobar' }],
+        message: 'Foobar',
+      });
+
+      expect(res).toBe('0abcdef');
+    });
+
+    it('aborts if rebase fails due to non-422', async () => {
+      git.pushCommitToRenovateRef.mockResolvedValueOnce();
+      git.listCommitTree.mockResolvedValueOnce([]);
+
+      const scope = httpMock.scope(githubApiHost);
+
+      initRepoMock(scope, 'some/repo');
+      await github.initRepo({ repository: 'some/repo' });
+
+      scope
+        .post('/repos/some/repo/git/trees')
+        .reply(200, { sha: '111' })
+        .post('/repos/some/repo/git/commits')
+        .reply(200, { sha: '222' })
+        .head('/repos/some/repo/git/refs/heads/foo/bar')
+        .reply(200)
+        .patch('/repos/some/repo/git/refs/heads/foo/bar')
+        .reply(404);
+
+      const res = await github.commitFiles({
+        branchName: 'foo/bar',
+        files: [{ type: 'addition', path: 'foo.bar', contents: 'foobar' }],
+        message: 'Foobar',
+      });
+
+      expect(res).toBeNull();
+    });
   });
 });

lib/modules/platform/github/index.ts

@@ -742,8 +742,9 @@ async function ensureBranchSha(branchName: string, sha: string): Promise<void> {
   const refUrl = `/repos/${config.repository}/git/refs/heads/${branchName}`;
 
   let branchExists = false;
+  let branchResult: undefined | HttpResponse<string>;
   try {
-    await githubApi.head(refUrl, { memCache: false });
+    branchResult = await githubApi.head(refUrl, { memCache: false });
     branchExists = true;
   } catch (err) {
     if (err.statusCode !== 404) {
@@ -752,8 +753,20 @@ async function ensureBranchSha(branchName: string, sha: string): Promise<void> {
   }
 
   if (branchExists) {
-    await githubApi.patchJson(refUrl, { body: { sha, force: true } });
-    return;
+    try {
+      await githubApi.patchJson(refUrl, { body: { sha, force: true } });
+      return;
+    } catch (err) {
+      if (err.err?.response?.statusCode === 422) {
+        logger.debug(
+          { branchResult, err },
+          'Branch update failed due to reference not existing - will try to create'
+        );
+      } else {
+        logger.warn({ refUrl, err, branchResult }, 'Error updating branch');
+        throw err;
+      }
+    }
   }
 
   await githubApi.postJson(`/repos/${config.repository}/git/refs`, {