diff --git a/lib/platform/azure/__snapshots__/index.spec.ts.snap b/lib/platform/azure/__snapshots__/index.spec.ts.snap
index c14a6a04039684514a706383815b24c95bcf18aa..d148e1eb6f74fbd4073f5ab48a8cad81f191cd9b 100644
--- a/lib/platform/azure/__snapshots__/index.spec.ts.snap
+++ b/lib/platform/azure/__snapshots__/index.spec.ts.snap
@@ -37,7 +37,6 @@ exports[`platform/azure deleteLabel() Should delete a label 1`] = `
 Array [
   Array [],
   Array [],
-  Array [],
 ]
 `;
 
@@ -165,7 +164,6 @@ Object {
 exports[`platform/azure initRepo should initialise the config for a repo 1`] = `
 Array [
   Array [],
-  Array [],
 ]
 `;
 
diff --git a/lib/platform/azure/index.spec.ts b/lib/platform/azure/index.spec.ts
index 1c234b6252d5bc9b83e4f59647a2de8d985ef76d..3b464d06980701d1de1ce2eafbb883ce19d94a1d 100644
--- a/lib/platform/azure/index.spec.ts
+++ b/lib/platform/azure/index.spec.ts
@@ -136,12 +136,6 @@ describe('platform/azure', () => {
           ]),
         } as any)
     );
-    azureApi.gitApi.mockImplementationOnce(
-      () =>
-        ({
-          getBranch: jest.fn(() => ({ commit: { commitId: '1234' } })),
-        } as any)
-    );
     azureHelper.getProjectAndRepo.mockImplementationOnce(() => ({
       project: 'some-repo',
       repo: 'some-repo',
@@ -779,7 +773,7 @@ describe('platform/azure', () => {
           } as any)
       );
       await azure.addAssignees(123, ['test@bonjour.fr', 'jyc', 'def']);
-      expect(azureApi.gitApi).toHaveBeenCalledTimes(4);
+      expect(azureApi.gitApi).toHaveBeenCalledTimes(3);
     });
   });
 
@@ -806,7 +800,7 @@ describe('platform/azure', () => {
           } as any)
       );
       await azure.addReviewers(123, ['test@bonjour.fr', 'jyc', 'def']);
-      expect(azureApi.gitApi).toHaveBeenCalledTimes(4);
+      expect(azureApi.gitApi).toHaveBeenCalledTimes(3);
     });
   });
 
diff --git a/lib/platform/azure/index.ts b/lib/platform/azure/index.ts
index 524d926c85d13e28f9f01ca8d2509085c406a3ef..2248bc4bdad713ae78036977ab921cf1389124b2 100644
--- a/lib/platform/azure/index.ts
+++ b/lib/platform/azure/index.ts
@@ -40,7 +40,6 @@ import { AzurePr } from './types';
 interface Config {
   repoForceRebase: boolean;
   mergeMethod: GitPullRequestMergeStrategy;
-  baseCommitSHA: string | undefined;
   baseBranch: string;
   defaultBranch: string;
   owner: string;
@@ -96,15 +95,6 @@ export async function getRepos(): Promise<string[]> {
   return repos.map((repo) => `${repo.project.name}/${repo.name}`);
 }
 
-async function getBranchCommit(fullBranchName: string): Promise<string> {
-  const azureApiGit = await azureApi.gitApi();
-  const commit = await azureApiGit.getBranch(
-    config.repoId,
-    azureHelper.getBranchNameWithoutRefsheadsPrefix(fullBranchName)!
-  );
-  return commit.commit.commitId;
-}
-
 export async function initRepo({
   repository,
   localDir,
@@ -130,7 +120,6 @@ export async function initRepo({
   config.defaultBranch = repo.defaultBranch.replace('refs/heads/', '');
   config.baseBranch = config.defaultBranch;
   logger.debug(`${repository} default branch = ${config.defaultBranch}`);
-  config.baseCommitSHA = await getBranchCommit(config.baseBranch);
   config.mergeMethod = await azureHelper.getMergeMethod(repo.id, names.project);
   config.repoForceRebase = false;
 
@@ -186,7 +175,6 @@ export function getRepoForceRebase(): Promise<boolean> {
 export async function setBaseBranch(branchName: string): Promise<string> {
   logger.debug(`Setting baseBranch to ${branchName}`);
   config.baseBranch = branchName;
-  delete config.baseCommitSHA;
   const baseBranchSha = await git.setBranch(branchName);
   return baseBranchSha;
 }
diff --git a/lib/platform/bitbucket/index.ts b/lib/platform/bitbucket/index.ts
index 46b20925b55ff0af1db06a188b95102388d58781..fc548e9b46e397eedd46f97a66dd0f29e5ff3f4b 100644
--- a/lib/platform/bitbucket/index.ts
+++ b/lib/platform/bitbucket/index.ts
@@ -177,7 +177,6 @@ export function getRepoForceRebase(): Promise<boolean> {
 export async function setBaseBranch(branchName: string): Promise<string> {
   logger.debug(`Setting baseBranch to ${branchName}`);
   config.baseBranch = branchName;
-  delete config.baseCommitSHA;
   const baseBranchSha = await git.setBranch(branchName);
   return baseBranchSha;
 }
@@ -777,7 +776,6 @@ export async function mergePr(
         },
       }
     );
-    delete config.baseCommitSHA;
     logger.debug('Automerging succeeded');
   } catch (err) /* istanbul ignore next */ {
     return false;
diff --git a/lib/platform/bitbucket/utils.ts b/lib/platform/bitbucket/utils.ts
index 6bb0c632193d7d17e058b12b2be31bb4ecc67e1b..4578ed5d6e6a2f34430f0067d408191d51060193 100644
--- a/lib/platform/bitbucket/utils.ts
+++ b/lib/platform/bitbucket/utils.ts
@@ -9,7 +9,6 @@ const bitbucketHttp = new BitbucketHttp();
 
 export interface Config {
   baseBranch: string;
-  baseCommitSHA: string;
   defaultBranch: string;
   has_issues: boolean;
   mergeMethod: string;
diff --git a/lib/platform/github/__snapshots__/index.spec.ts.snap b/lib/platform/github/__snapshots__/index.spec.ts.snap
index 9d025fac703ab99253e7a531643308fd2904a711..8694755cc923de746c5edb6279e0fa4e33a9d400 100644
--- a/lib/platform/github/__snapshots__/index.spec.ts.snap
+++ b/lib/platform/github/__snapshots__/index.spec.ts.snap
@@ -12,6 +12,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -26,7 +29,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -63,6 +66,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -77,7 +83,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -122,6 +128,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -136,7 +145,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -181,6 +190,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -195,7 +207,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -301,6 +313,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -315,7 +330,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -352,6 +367,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -366,7 +384,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -400,6 +418,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -414,7 +435,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -505,6 +526,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -519,7 +543,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -610,6 +634,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -624,7 +651,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -704,6 +731,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -718,7 +748,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -795,6 +825,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -809,7 +842,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -886,6 +919,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -900,7 +936,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -988,6 +1024,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -1002,7 +1041,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -1812,6 +1851,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -1826,7 +1868,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -1884,6 +1926,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -1898,7 +1943,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2095,6 +2140,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2109,7 +2157,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2117,17 +2165,6 @@ Array [
     "method": "POST",
     "url": "https://api.github.com/graphql",
   },
-  Object {
-    "headers": Object {
-      "accept": "application/vnd.github.v3+json",
-      "accept-encoding": "gzip, deflate",
-      "authorization": "token abc123",
-      "host": "api.github.com",
-      "user-agent": "https://github.com/renovatebot/renovate",
-    },
-    "method": "GET",
-    "url": "https://api.github.com/repos/some/repo/git/refs/heads/master",
-  },
   Object {
     "headers": Object {
       "accept": "application/vnd.github.v3+json",
@@ -2329,6 +2366,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2343,7 +2383,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2388,6 +2428,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2402,7 +2445,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2425,6 +2468,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2439,7 +2485,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2462,6 +2508,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2476,7 +2525,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2521,6 +2570,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2535,7 +2587,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2580,6 +2632,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2594,7 +2649,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2639,6 +2694,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2653,7 +2711,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2698,6 +2756,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2712,7 +2773,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2757,6 +2818,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2771,7 +2835,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2805,6 +2869,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2819,7 +2886,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -2876,6 +2943,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -2890,7 +2960,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -3057,6 +3127,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -3071,7 +3144,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -3192,6 +3265,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -3206,7 +3282,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -3386,6 +3462,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -3400,7 +3479,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -3578,6 +3657,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -3592,7 +3674,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -3754,6 +3836,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -3768,7 +3853,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -3952,6 +4037,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -3966,7 +4054,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "github.company.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4491,6 +4579,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4505,7 +4596,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4513,17 +4604,6 @@ Array [
     "method": "POST",
     "url": "https://api.github.com/graphql",
   },
-  Object {
-    "headers": Object {
-      "accept": "application/vnd.github.v3+json",
-      "accept-encoding": "gzip, deflate",
-      "authorization": "token abc123",
-      "host": "api.github.com",
-      "user-agent": "https://github.com/renovatebot/renovate",
-    },
-    "method": "GET",
-    "url": "https://api.github.com/repos/some/repo/git/refs/heads/master",
-  },
   Object {
     "headers": Object {
       "accept": "application/vnd.github.v3+json",
@@ -4568,6 +4648,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4582,7 +4665,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4612,6 +4695,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4626,7 +4712,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4656,6 +4742,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4670,7 +4759,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4700,6 +4789,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4714,7 +4806,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4737,6 +4829,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4751,7 +4846,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4785,6 +4880,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4799,7 +4897,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4822,6 +4920,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4836,7 +4937,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4866,6 +4967,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4880,7 +4984,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4888,17 +4992,6 @@ Array [
     "method": "POST",
     "url": "https://api.github.com/graphql",
   },
-  Object {
-    "headers": Object {
-      "accept": "application/vnd.github.v3+json",
-      "accept-encoding": "gzip, deflate",
-      "authorization": "token abc123",
-      "host": "api.github.com",
-      "user-agent": "https://github.com/renovatebot/renovate",
-    },
-    "method": "GET",
-    "url": "https://api.github.com/repos/some/repo/git/refs/heads/master",
-  },
   Object {
     "headers": Object {
       "accept": "application/vnd.github.v3+json",
@@ -4957,6 +5050,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -4971,7 +5067,7 @@ Array [
       "accept": "application/vnd.github.machine-man-preview+json, application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -4994,6 +5090,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5008,7 +5107,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5031,6 +5130,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5045,7 +5147,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5124,6 +5226,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5138,7 +5243,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5203,6 +5308,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5217,7 +5325,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5254,6 +5362,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5268,7 +5379,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5305,6 +5416,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5319,7 +5433,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5356,6 +5470,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5370,7 +5487,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5407,6 +5524,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5421,7 +5541,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5455,6 +5575,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5469,7 +5592,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
@@ -5539,6 +5662,9 @@ Array [
           },
           "defaultBranchRef": Object {
             "name": null,
+            "target": Object {
+              "oid": null,
+            },
           },
           "isArchived": null,
           "isFork": null,
@@ -5553,7 +5679,7 @@ Array [
       "accept": "application/vnd.github.v3+json",
       "accept-encoding": "gzip, deflate",
       "authorization": "token abc123",
-      "content-length": "280",
+      "content-length": "330",
       "content-type": "application/json",
       "host": "api.github.com",
       "user-agent": "https://github.com/renovatebot/renovate",
diff --git a/lib/platform/github/index.spec.ts b/lib/platform/github/index.spec.ts
index 6007e665316bf30e508890c1d2117de5c754315a..95397b73ef38da970ea348130f1b08e39fdb66a5 100644
--- a/lib/platform/github/index.spec.ts
+++ b/lib/platform/github/index.spec.ts
@@ -165,6 +165,9 @@ describe('platform/github', () => {
           squashMergeAllowed: true,
           defaultBranchRef: {
             name: 'master',
+            target: {
+              oid: '1234',
+            },
           },
         },
       },
@@ -190,17 +193,13 @@ describe('platform/github', () => {
             squashMergeAllowed: true,
             defaultBranchRef: {
               name: 'master',
+              target: {
+                oid: '1234',
+              },
             },
           },
         },
       })
-      // getBranchCommit
-      .get(`/repos/${repository}/git/refs/heads/master`)
-      .reply(200, {
-        object: {
-          sha: '1234',
-        },
-      })
       // getRepos
       .get('/user/repos?per_page=100')
       .reply(200, forkedRepo ? [{ full_name: forkedRepo }] : [])
@@ -280,6 +279,9 @@ describe('platform/github', () => {
               squashMergeAllowed: true,
               defaultBranchRef: {
                 name: 'master',
+                target: {
+                  oid: '1234',
+                },
               },
             },
           },
@@ -305,6 +307,9 @@ describe('platform/github', () => {
               squashMergeAllowed: false,
               defaultBranchRef: {
                 name: 'master',
+                target: {
+                  oid: '1234',
+                },
               },
             },
           },
@@ -324,6 +329,9 @@ describe('platform/github', () => {
             repository: {
               defaultBranchRef: {
                 name: 'master',
+                target: {
+                  oid: '1234',
+                },
               },
             },
           },
@@ -345,6 +353,9 @@ describe('platform/github', () => {
               nameWithOwner: 'some/repo',
               defaultBranchRef: {
                 name: 'master',
+                target: {
+                  oid: '1234',
+                },
               },
             },
           },
@@ -375,6 +386,9 @@ describe('platform/github', () => {
               nameWithOwner: 'some/other',
               defaultBranchRef: {
                 name: 'master',
+                target: {
+                  oid: '1234',
+                },
               },
             },
           },
@@ -1659,8 +1673,7 @@ describe('platform/github', () => {
         .post('/graphql')
         .reply(200, graphqlOpenPullRequests)
         .post('/graphql')
-        .reply(200, graphqlClosedPullRequests)
-        .get('/repos/some/repo/git/refs/heads/master');
+        .reply(200, graphqlClosedPullRequests);
       await github.initRepo({
         repository: 'some/repo',
       } as any);
diff --git a/lib/platform/github/index.ts b/lib/platform/github/index.ts
index 3f32448b4a87f419e06df4a99f5ffcd2429cb2c3..6f42a5bfee9882163bc1772eb2edb26742914933 100644
--- a/lib/platform/github/index.ts
+++ b/lib/platform/github/index.ts
@@ -162,32 +162,6 @@ async function getBranchProtection(
   return res.body;
 }
 
-// Return the commit SHA for a branch
-async function getBranchCommit(branchName: string): Promise<string> {
-  try {
-    const res = await githubApi.getJson<{ object: { sha: string } }>(
-      `repos/${config.repository}/git/refs/heads/${escapeHash(branchName)}`
-    );
-    return res.body.object.sha;
-  } catch (err) /* istanbul ignore next */ {
-    logger.debug({ err }, 'Error getting branch commit');
-    if (err.statusCode === 404) {
-      throw new Error(REPOSITORY_CHANGED);
-    }
-    if (err.statusCode === 409) {
-      throw new Error(REPOSITORY_EMPTY);
-    }
-    throw err;
-  }
-}
-
-async function getBaseCommitSHA(): Promise<string> {
-  if (!config.baseCommitSHA) {
-    config.baseCommitSHA = await getBranchCommit(config.baseBranch);
-  }
-  return config.baseCommitSHA;
-}
-
 // Initialize GitHub by getting base branch and SHA
 export async function initRepo({
   endpoint,
@@ -229,6 +203,9 @@ export async function initRepo({
         squashMergeAllowed
         defaultBranchRef {
           name
+          target {
+            oid
+          }
         }
       }
     }`
@@ -350,8 +327,7 @@ export async function initRepo({
     logger.debug('Bot is in forkMode');
     config.forkToken = forkToken;
     // Save parent SHA then delete
-    const parentSha = await getBaseCommitSHA();
-    config.baseCommitSHA = null;
+    const parentSha = repo.defaultBranchRef.target.oid;
     // save parent name then delete
     config.parentRepo = config.repository;
     config.repository = null;
@@ -502,7 +478,6 @@ export async function getRepoForceRebase(): Promise<boolean> {
 // istanbul ignore next
 export async function setBaseBranch(branchName: string): Promise<string> {
   config.baseBranch = branchName;
-  config.baseCommitSHA = null;
   const baseBranchSha = await git.setBranch(branchName);
   return baseBranchSha;
 }
@@ -1612,8 +1587,6 @@ export async function mergePr(
     }
   }
   logger.debug({ pr: prNo }, 'PR merged');
-  // Update base branch SHA
-  config.baseCommitSHA = null;
   // Delete branch
   await deleteBranch(branchName);
   return true;
diff --git a/lib/platform/github/types.ts b/lib/platform/github/types.ts
index fd234e7f5de36cfcb6e5eb8cb3132c0c672ce890..49eb596fc30610dd4a31d6186296ee8db098dd27 100644
--- a/lib/platform/github/types.ts
+++ b/lib/platform/github/types.ts
@@ -30,7 +30,6 @@ export interface LocalRepoConfig {
   prReviewsRequired: boolean;
   repoForceRebase?: boolean;
   parentRepo: string;
-  baseCommitSHA: string | null;
   forkMode?: boolean;
   forkToken?: string;
   closedPrList: PrList | null;
@@ -60,5 +59,8 @@ export interface GhRepo {
   squashMergeAllowed: boolean;
   defaultBranchRef: {
     name: string;
+    target: {
+      oid: string;
+    };
   };
 }