improve description for fetch-depth (#301)

CHANGELOG.md

@@ -1,6 +1,20 @@
 # Changelog
 
+## v2.3.1
+
+- [Fix default branch resolution for .wiki and when using SSH](https://github.com/actions/checkout/pull/284)
+
+
+## v2.3.0
+
+- [Fallback to the default branch](https://github.com/actions/checkout/pull/278)
+
+## v2.2.0
+
+- [Fetch all history for all tags and branches when fetch-depth=0](https://github.com/actions/checkout/pull/258)
+
 ## v2.1.1
+
 - Changes to support GHES ([here](https://github.com/actions/checkout/pull/236) and [here](https://github.com/actions/checkout/pull/248))
 
 ## v2.1.0

README.md

@@ -6,7 +6,7 @@
 
 This action checks-out your repository under `$GITHUB_WORKSPACE`, so your workflow can access it.
 
-Only a single commit is fetched by default, for the ref/SHA that triggered the workflow. Set `fetch-depth` to fetch more history. Refer [here](https://help.github.com/en/articles/events-that-trigger-workflows) to learn which commit `$GITHUB_SHA` points to for different events.
+Only a single commit is fetched by default, for the ref/SHA that triggered the workflow. Set `fetch-depth: 0` to fetch all history for all branches and tags. Refer [here](https://help.github.com/en/articles/events-that-trigger-workflows) to learn which commit `$GITHUB_SHA` points to for different events.
 
 The auth token is persisted in the local git config. This enables your scripts to run authenticated git commands. The token is removed during post-job cleanup. Set `persist-credentials: false` to opt-out.
 
@@ -42,7 +42,7 @@ Refer [here](https://github.com/actions/checkout/blob/v1/README.md) for previous
 
     # The branch, tag or SHA to checkout. When checking out the repository that
     # triggered a workflow, this defaults to the reference or SHA for that event.
-    # Otherwise, defaults to `master`.
+    # Otherwise, uses the default branch.
     ref: ''
 
     # Personal access token (PAT) used to fetch the repository. The PAT is configured
@@ -89,7 +89,7 @@ Refer [here](https://github.com/actions/checkout/blob/v1/README.md) for previous
     # Default: true
     clean: ''
 
-    # Number of commits to fetch. 0 indicates all history.
+    # Number of commits to fetch. 0 indicates all history for all branches and tags.
     # Default: 1
     fetch-depth: ''
 
@@ -110,6 +110,7 @@ Refer [here](https://github.com/actions/checkout/blob/v1/README.md) for previous
 
 # Scenarios
 
+- [Fetch all history for all tags and branches](#Fetch-all-history-for-all-tags-and-branches)
 - [Checkout a different branch](#Checkout-a-different-branch)
 - [Checkout HEAD^](#Checkout-HEAD)
 - [Checkout multiple repos (side by side)](#Checkout-multiple-repos-side-by-side)
@@ -117,9 +118,14 @@ Refer [here](https://github.com/actions/checkout/blob/v1/README.md) for previous
 - [Checkout multiple repos (private)](#Checkout-multiple-repos-private)
 - [Checkout pull request HEAD commit instead of merge commit](#Checkout-pull-request-HEAD-commit-instead-of-merge-commit)
 - [Checkout pull request on closed event](#Checkout-pull-request-on-closed-event)
-- [Fetch all tags](#Fetch-all-tags)
+
-- [Fetch all branches](#Fetch-all-branches)
+## Fetch all history for all tags and branches
-- [Fetch all history for all tags and branches](#Fetch-all-history-for-all-tags-and-branches)
+
+```yaml
+- uses: actions/checkout@v2
+  with:
+    fetch-depth: 0
+```
 
 ## Checkout a different branch
 
@@ -207,29 +213,6 @@ jobs:
       - uses: actions/checkout@v2
 ```
 
-## Fetch all tags
-
-```yaml
-- uses: actions/checkout@v2
-- run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*
-```
-
-## Fetch all branches
-
-```yaml
-- uses: actions/checkout@v2
-- run: |
-    git fetch --no-tags --prune --depth=1 origin +refs/heads/*:refs/remotes/origin/*
-```
-
-## Fetch all history for all tags and branches
-
-```yaml
-- uses: actions/checkout@v2
-- run: |
-    git fetch --prune --unshallow
-```
-
 # License
 
 The scripts and documentation in this project are released under the [MIT License](LICENSE)

__test__/git-auth-helper.test.ts

@@ -714,6 +714,7 @@ async function setup(testName: string): Promise<void> {
     ),
     env: {},
     fetch: jest.fn(),
+    getDefaultBranch: jest.fn(),
     getWorkingDirectory: jest.fn(() => workspace),
     init: jest.fn(),
     isDetached: jest.fn(),
@@ -722,9 +723,11 @@ async function setup(testName: string): Promise<void> {
     log1: jest.fn(),
     remoteAdd: jest.fn(),
     removeEnvironmentVariable: jest.fn((name: string) => delete git.env[name]),
+    revParse: jest.fn(),
     setEnvironmentVariable: jest.fn((name: string, value: string) => {
       git.env[name] = value
     }),
+    shaExists: jest.fn(),
     submoduleForeach: jest.fn(async () => {
       return ''
     }),

__test__/git-directory-helper.test.ts

@@ -9,6 +9,7 @@ const testWorkspace = path.join(__dirname, '_temp', 'git-directory-helper')
 let repositoryPath: string
 let repositoryUrl: string
 let clean: boolean
+let ref: string
 let git: IGitCommandManager
 
 describe('git-directory-helper tests', () => {
@@ -41,7 +42,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -63,7 +65,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -88,7 +91,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -109,7 +113,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -137,7 +142,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -163,7 +169,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       differentRepositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -187,7 +194,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -212,7 +220,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -236,7 +245,8 @@ describe('git-directory-helper tests', () => {
       undefined,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -260,7 +270,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -290,7 +301,8 @@ describe('git-directory-helper tests', () => {
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
@@ -305,29 +317,66 @@ describe('git-directory-helper tests', () => {
     expect(git.tryReset).not.toHaveBeenCalled()
   })
 
-  const removesRemoteBranches = 'removes local branches'
+  const removesAncestorRemoteBranch = 'removes ancestor remote branch'
-  it(removesRemoteBranches, async () => {
+  it(removesAncestorRemoteBranch, async () => {
     // Arrange
-    await setup(removesRemoteBranches)
+    await setup(removesAncestorRemoteBranch)
     await fs.promises.writeFile(path.join(repositoryPath, 'my-file'), '')
     const mockBranchList = git.branchList as jest.Mock<any, any>
     mockBranchList.mockImplementation(async (remote: boolean) => {
-      return remote ? ['remote-branch-1', 'remote-branch-2'] : []
+      return remote ? ['origin/remote-branch-1', 'origin/remote-branch-2'] : []
     })
+    ref = 'remote-branch-1/conflict'
 
     // Act
     await gitDirectoryHelper.prepareExistingDirectory(
       git,
       repositoryPath,
       repositoryUrl,
-      clean
+      clean,
+      ref
     )
 
     // Assert
     const files = await fs.promises.readdir(repositoryPath)
     expect(files.sort()).toEqual(['.git', 'my-file'])
-    expect(git.branchDelete).toHaveBeenCalledWith(true, 'remote-branch-1')
+    expect(git.branchDelete).toHaveBeenCalledTimes(1)
-    expect(git.branchDelete).toHaveBeenCalledWith(true, 'remote-branch-2')
+    expect(git.branchDelete).toHaveBeenCalledWith(
+      true,
+      'origin/remote-branch-1'
+    )
+  })
+
+  const removesDescendantRemoteBranches = 'removes descendant remote branch'
+  it(removesDescendantRemoteBranches, async () => {
+    // Arrange
+    await setup(removesDescendantRemoteBranches)
+    await fs.promises.writeFile(path.join(repositoryPath, 'my-file'), '')
+    const mockBranchList = git.branchList as jest.Mock<any, any>
+    mockBranchList.mockImplementation(async (remote: boolean) => {
+      return remote
+        ? ['origin/remote-branch-1/conflict', 'origin/remote-branch-2']
+        : []
+    })
+    ref = 'remote-branch-1'
+
+    // Act
+    await gitDirectoryHelper.prepareExistingDirectory(
+      git,
+      repositoryPath,
+      repositoryUrl,
+      clean,
+      ref
+    )
+
+    // Assert
+    const files = await fs.promises.readdir(repositoryPath)
+    expect(files.sort()).toEqual(['.git', 'my-file'])
+    expect(git.branchDelete).toHaveBeenCalledTimes(1)
+    expect(git.branchDelete).toHaveBeenCalledWith(
+      true,
+      'origin/remote-branch-1/conflict'
+    )
   })
 })
 
@@ -344,6 +393,9 @@ async function setup(testName: string): Promise<void> {
   // Clean
   clean = true
 
+  // Ref
+  ref = ''
+
   // Git command manager
   git = {
     branchDelete: jest.fn(),
@@ -356,6 +408,7 @@ async function setup(testName: string): Promise<void> {
     config: jest.fn(),
     configExists: jest.fn(),
     fetch: jest.fn(),
+    getDefaultBranch: jest.fn(),
     getWorkingDirectory: jest.fn(() => repositoryPath),
     init: jest.fn(),
     isDetached: jest.fn(),
@@ -364,7 +417,9 @@ async function setup(testName: string): Promise<void> {
     log1: jest.fn(),
     remoteAdd: jest.fn(),
     removeEnvironmentVariable: jest.fn(),
+    revParse: jest.fn(),
     setEnvironmentVariable: jest.fn(),
+    shaExists: jest.fn(),
     submoduleForeach: jest.fn(),
     submoduleSync: jest.fn(),
     submoduleUpdate: jest.fn(),

__test__/input-helper.test.ts

@@ -110,13 +110,6 @@ describe('input-helper tests', () => {
     )
   })
 
-  it('sets correct default ref/sha for other repo', () => {
-    inputs.repository = 'some-owner/some-other-repo'
-    const settings: IGitSourceSettings = inputHelper.getInputs()
-    expect(settings.ref).toBe('refs/heads/master')
-    expect(settings.commit).toBeFalsy()
-  })
-
   it('sets ref to empty when explicit sha', () => {
     inputs.ref = '1111111111222222222233333333334444444444'
     const settings: IGitSourceSettings = inputHelper.getInputs()

__test__/verify-no-unstaged-changes.sh

@@ -12,6 +12,6 @@ if [[ "$(git status --porcelain)" != "" ]]; then
     echo ----------------------------------------
     echo Troubleshooting
     echo ----------------------------------------
-    echo "::error::Unstaged changes detected. Locally try running: git clean -ffdx && npm ci && npm run all"
+    echo "::error::Unstaged changes detected. Locally try running: git clean -ffdx && npm ci && npm run format && npm run build"
     exit 1
 fi

action.yml

@@ -8,7 +8,7 @@ inputs:
     description: >
       The branch, tag or SHA to checkout. When checking out the repository that
       triggered a workflow, this defaults to the reference or SHA for that
-      event.  Otherwise, defaults to `master`.
+      event.  Otherwise, uses the default branch.
   token:
     description: >
       Personal access token (PAT) used to fetch the repository. The PAT is configured
@@ -54,7 +54,7 @@ inputs:
     description: 'Whether to execute `git clean -ffdx && git reset --hard HEAD` before fetching'
     default: true
   fetch-depth:
-    description: 'Number of commits to fetch. 0 indicates all history.'
+    description: 'Number of commits to fetch. 0 indicates all history for all branches and tags.'
     default: 1
   lfs:
     description: 'Whether to download Git-LFS files'

adrs/0153-checkout-v2.md

@@ -70,7 +70,7 @@ We want to take this opportunity to make behavioral changes, from v1. This docum
     description: 'Whether to execute `git clean -ffdx && git reset --hard HEAD` before fetching'
     default: true
   fetch-depth:
-    description: 'Number of commits to fetch. 0 indicates all history.'
+    description: 'Number of commits to fetch. 0 indicates all history for all tags and branches.'
     default: 1
   lfs:
     description: 'Whether to download Git-LFS files'

dist/index.js

@@ -3359,7 +3359,7 @@ module.exports = {"name":"@octokit/rest","version":"16.43.1","publishConfig":{"a
 /***/ }),
 
 /***/ 227:
-/***/ (function(__unusedmodule, exports) {
+/***/ (function(__unusedmodule, exports, __webpack_require__) {
 
 "use strict";
 
@@ -3372,7 +3372,18 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
         step((generator = generator.apply(thisArg, _arguments || [])).next());
     });
 };
+var __importStar = (this && this.__importStar) || function (mod) {
+    if (mod && mod.__esModule) return mod;
+    var result = {};
+    if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) result[k] = mod[k];
+    result["default"] = mod;
+    return result;
+};
 Object.defineProperty(exports, "__esModule", { value: true });
+const url_1 = __webpack_require__(835);
+const core = __importStar(__webpack_require__(470));
+const github = __importStar(__webpack_require__(469));
+exports.tagsRefSpec = '+refs/tags/*:refs/tags/*';
 function getCheckoutInfo(git, ref, commit) {
     return __awaiter(this, void 0, void 0, function* () {
         if (!git) {
@@ -3419,6 +3430,15 @@ function getCheckoutInfo(git, ref, commit) {
     });
 }
 exports.getCheckoutInfo = getCheckoutInfo;
+function getRefSpecForAllHistory(ref, commit) {
+    const result = ['+refs/heads/*:refs/remotes/origin/*', exports.tagsRefSpec];
+    if (ref && ref.toUpperCase().startsWith('REFS/PULL/')) {
+        const branch = ref.substring('refs/pull/'.length);
+        result.push(`+${commit || ref}:refs/remotes/pull/${branch}`);
+    }
+    return result;
+}
+exports.getRefSpecForAllHistory = getRefSpecForAllHistory;
 function getRefSpec(ref, commit) {
     if (!ref && !commit) {
         throw new Error('Args ref and commit cannot both be empty');
@@ -3468,6 +3488,129 @@ function getRefSpec(ref, commit) {
     }
 }
 exports.getRefSpec = getRefSpec;
+/**
+ * Tests whether the initial fetch created the ref at the expected commit
+ */
+function testRef(git, ref, commit) {
+    return __awaiter(this, void 0, void 0, function* () {
+        if (!git) {
+            throw new Error('Arg git cannot be empty');
+        }
+        if (!ref && !commit) {
+            throw new Error('Args ref and commit cannot both be empty');
+        }
+        // No SHA? Nothing to test
+        if (!commit) {
+            return true;
+        }
+        // SHA only?
+        else if (!ref) {
+            return yield git.shaExists(commit);
+        }
+        const upperRef = ref.toUpperCase();
+        // refs/heads/
+        if (upperRef.startsWith('REFS/HEADS/')) {
+            const branch = ref.substring('refs/heads/'.length);
+            return ((yield git.branchExists(true, `origin/${branch}`)) &&
+                commit === (yield git.revParse(`refs/remotes/origin/${branch}`)));
+        }
+        // refs/pull/
+        else if (upperRef.startsWith('REFS/PULL/')) {
+            // Assume matches because fetched using the commit
+            return true;
+        }
+        // refs/tags/
+        else if (upperRef.startsWith('REFS/TAGS/')) {
+            const tagName = ref.substring('refs/tags/'.length);
+            return ((yield git.tagExists(tagName)) && commit === (yield git.revParse(ref)));
+        }
+        // Unexpected
+        else {
+            core.debug(`Unexpected ref format '${ref}' when testing ref info`);
+            return true;
+        }
+    });
+}
+exports.testRef = testRef;
+function checkCommitInfo(token, commitInfo, repositoryOwner, repositoryName, ref, commit) {
+    return __awaiter(this, void 0, void 0, function* () {
+        try {
+            // GHES?
+            if (isGhes()) {
+                return;
+            }
+            // Auth token?
+            if (!token) {
+                return;
+            }
+            // Public PR synchronize, for workflow repo?
+            if (fromPayload('repository.private') !== false ||
+                github.context.eventName !== 'pull_request' ||
+                fromPayload('action') !== 'synchronize' ||
+                repositoryOwner !== github.context.repo.owner ||
+                repositoryName !== github.context.repo.repo ||
+                ref !== github.context.ref ||
+                !ref.startsWith('refs/pull/') ||
+                commit !== github.context.sha) {
+                return;
+            }
+            // Head SHA
+            const expectedHeadSha = fromPayload('after');
+            if (!expectedHeadSha) {
+                core.debug('Unable to determine head sha');
+                return;
+            }
+            // Base SHA
+            const expectedBaseSha = fromPayload('pull_request.base.sha');
+            if (!expectedBaseSha) {
+                core.debug('Unable to determine base sha');
+                return;
+            }
+            // Expected message?
+            const expectedMessage = `Merge ${expectedHeadSha} into ${expectedBaseSha}`;
+            if (commitInfo.indexOf(expectedMessage) >= 0) {
+                return;
+            }
+            // Extract details from message
+            const match = commitInfo.match(/Merge ([0-9a-f]{40}) into ([0-9a-f]{40})/);
+            if (!match) {
+                core.debug('Unexpected message format');
+                return;
+            }
+            // Post telemetry
+            const actualHeadSha = match[1];
+            if (actualHeadSha !== expectedHeadSha) {
+                core.debug(`Expected head sha ${expectedHeadSha}; actual head sha ${actualHeadSha}`);
+                const octokit = new github.GitHub(token, {
+                    userAgent: `actions-checkout-tracepoint/1.0 (code=STALE_MERGE;owner=${repositoryOwner};repo=${repositoryName};pr=${fromPayload('number')};run_id=${process.env['GITHUB_RUN_ID']};expected_head_sha=${expectedHeadSha};actual_head_sha=${actualHeadSha})`
+                });
+                yield octokit.repos.get({ owner: repositoryOwner, repo: repositoryName });
+            }
+        }
+        catch (err) {
+            core.debug(`Error when validating commit info: ${err.stack}`);
+        }
+    });
+}
+exports.checkCommitInfo = checkCommitInfo;
+function fromPayload(path) {
+    return select(github.context.payload, path);
+}
+function select(obj, path) {
+    if (!obj) {
+        return undefined;
+    }
+    const i = path.indexOf('.');
+    if (i < 0) {
+        return obj[path];
+    }
+    const key = path.substr(0, i);
+    return select(obj[key], path.substr(i + 1));
+}
+function isGhes() {
+    const ghUrl = new url_1.URL(process.env['GITHUB_SERVER_URL'] || 'https://github.com');
+    return ghUrl.hostname.toUpperCase() !== 'GITHUB.COM';
+}
 
 
 /***/ }),
@@ -5545,6 +5688,7 @@ const exec = __importStar(__webpack_require__(986));
 const fshelper = __importStar(__webpack_require__(618));
 const io = __importStar(__webpack_require__(1));
 const path = __importStar(__webpack_require__(622));
+const refHelper = __importStar(__webpack_require__(227));
 const regexpHelper = __importStar(__webpack_require__(528));
 const retryHelper = __importStar(__webpack_require__(587));
 const git_version_1 = __webpack_require__(559);
@@ -5660,18 +5804,14 @@ class GitCommandManager {
             return output.exitCode === 0;
         });
     }
-    fetch(fetchDepth, refSpec) {
+    fetch(refSpec, fetchDepth) {
         return __awaiter(this, void 0, void 0, function* () {
-            const args = [
+            const args = ['-c', 'protocol.version=2', 'fetch'];
-                '-c',
+            if (!refSpec.some(x => x === refHelper.tagsRefSpec)) {
-                'protocol.version=2',
+                args.push('--no-tags');
-                'fetch',
+            }
-                '--no-tags',
+            args.push('--prune', '--progress', '--no-recurse-submodules');
-                '--prune',
+            if (fetchDepth && fetchDepth > 0) {
-                '--progress',
-                '--no-recurse-submodules'
-            ];
-            if (fetchDepth > 0) {
                 args.push(`--depth=${fetchDepth}`);
             }
             else if (fshelper.fileExistsSync(path.join(this.workingDirectory, '.git', 'shallow'))) {
@@ -5687,6 +5827,33 @@ class GitCommandManager {
             }));
         });
     }
+    getDefaultBranch(repositoryUrl) {
+        return __awaiter(this, void 0, void 0, function* () {
+            let output;
+            yield retryHelper.execute(() => __awaiter(this, void 0, void 0, function* () {
+                output = yield this.execGit([
+                    'ls-remote',
+                    '--quiet',
+                    '--exit-code',
+                    '--symref',
+                    repositoryUrl,
+                    'HEAD'
+                ]);
+            }));
+            if (output) {
+                // Satisfy compiler, will always be set
+                for (let line of output.stdout.trim().split('\n')) {
+                    line = line.trim();
+                    if (line.startsWith('ref:') || line.endsWith('HEAD')) {
+                        return line
+                            .substr('ref:'.length, line.length - 'ref:'.length - 'HEAD'.length)
+                            .trim();
+                    }
+                }
+            }
+            throw new Error('Unexpected output when retrieving default branch');
+        });
+    }
     getWorkingDirectory() {
         return this.workingDirectory;
     }
@@ -5718,7 +5885,8 @@ class GitCommandManager {
     }
     log1() {
         return __awaiter(this, void 0, void 0, function* () {
-            yield this.execGit(['log', '-1']);
+            const output = yield this.execGit(['log', '-1']);
+            return output.stdout;
         });
     }
     remoteAdd(remoteName, remoteUrl) {
@@ -5729,9 +5897,28 @@ class GitCommandManager {
     removeEnvironmentVariable(name) {
         delete this.gitEnv[name];
     }
+    /**
+     * Resolves a ref to a SHA. For a branch or lightweight tag, the commit SHA is returned.
+     * For an annotated tag, the tag SHA is returned.
+     * @param {string} ref  For example: 'refs/heads/master' or '/refs/tags/v1'
+     * @returns {Promise<string>}
+     */
+    revParse(ref) {
+        return __awaiter(this, void 0, void 0, function* () {
+            const output = yield this.execGit(['rev-parse', ref]);
+            return output.stdout.trim();
+        });
+    }
     setEnvironmentVariable(name, value) {
         this.gitEnv[name] = value;
     }
+    shaExists(sha) {
+        return __awaiter(this, void 0, void 0, function* () {
+            const args = ['rev-parse', '--verify', '--quiet', `${sha}^{object}`];
+            const output = yield this.execGit(args, true);
+            return output.exitCode === 0;
+        });
+    }
     submoduleForeach(command, recursive) {
         return __awaiter(this, void 0, void 0, function* () {
             const args = ['submodule', 'foreach'];
@@ -5970,7 +6157,7 @@ function getSource(settings) {
         core.endGroup();
         // Prepare existing directory, otherwise recreate
         if (isExisting) {
-            yield gitDirectoryHelper.prepareExistingDirectory(git, settings.repositoryPath, repositoryUrl, settings.clean);
+            yield gitDirectoryHelper.prepareExistingDirectory(git, settings.repositoryPath, repositoryUrl, settings.clean, settings.ref);
         }
         if (!git) {
             // Downloading using REST API
@@ -6006,14 +6193,38 @@ function getSource(settings) {
             core.startGroup('Setting up auth');
             yield authHelper.configureAuth();
             core.endGroup();
+            // Determine the default branch
+            if (!settings.ref && !settings.commit) {
+                core.startGroup('Determining the default branch');
+                if (settings.sshKey) {
+                    settings.ref = yield git.getDefaultBranch(repositoryUrl);
+                }
+                else {
+                    settings.ref = yield githubApiHelper.getDefaultBranch(settings.authToken, settings.repositoryOwner, settings.repositoryName);
+                }
+                core.endGroup();
+            }
             // LFS install
             if (settings.lfs) {
                 yield git.lfsInstall();
             }
             // Fetch
             core.startGroup('Fetching the repository');
-            const refSpec = refHelper.getRefSpec(settings.ref, settings.commit);
+            if (settings.fetchDepth <= 0) {
-            yield git.fetch(settings.fetchDepth, refSpec);
+                // Fetch all branches and tags
+                let refSpec = refHelper.getRefSpecForAllHistory(settings.ref, settings.commit);
+                yield git.fetch(refSpec);
+                // When all history is fetched, the ref we're interested in may have moved to a different
+                // commit (push or force push). If so, fetch again with a targeted refspec.
+                if (!(yield refHelper.testRef(git, settings.ref, settings.commit))) {
+                    refSpec = refHelper.getRefSpec(settings.ref, settings.commit);
+                    yield git.fetch(refSpec);
+                }
+            }
+            else {
+                const refSpec = refHelper.getRefSpec(settings.ref, settings.commit);
+                yield git.fetch(refSpec, settings.fetchDepth);
+            }
             core.endGroup();
             // Checkout info
             core.startGroup('Determining the checkout info');
@@ -6057,7 +6268,9 @@ function getSource(settings) {
                 }
             }
             // Dump some info about the checked out commit
-            yield git.log1();
+            const commitInfo = yield git.log1();
+            // Check for incorrect pull request merge commit
+            yield refHelper.checkCommitInfo(settings.authToken, commitInfo, settings.repositoryOwner, settings.repositoryName, settings.ref, settings.commit);
         }
         finally {
             // Remove auth
@@ -7362,7 +7575,7 @@ const fs = __importStar(__webpack_require__(747));
 const fsHelper = __importStar(__webpack_require__(618));
 const io = __importStar(__webpack_require__(1));
 const path = __importStar(__webpack_require__(622));
-function prepareExistingDirectory(git, repositoryPath, repositoryUrl, clean) {
+function prepareExistingDirectory(git, repositoryPath, repositoryUrl, clean, ref) {
     return __awaiter(this, void 0, void 0, function* () {
         assert.ok(repositoryPath, 'Expected repositoryPath to be defined');
         assert.ok(repositoryUrl, 'Expected repositoryUrl to be defined');
@@ -7402,10 +7615,24 @@ function prepareExistingDirectory(git, repositoryPath, repositoryUrl, clean) {
                 for (const branch of branches) {
                     yield git.branchDelete(false, branch);
                 }
-                // Remove all refs/remotes/origin/* to avoid conflicts
+                // Remove any conflicting refs/remotes/origin/*
-                branches = yield git.branchList(true);
+                // Example 1: Consider ref is refs/heads/foo and previously fetched refs/remotes/origin/foo/bar
-                for (const branch of branches) {
+                // Example 2: Consider ref is refs/heads/foo/bar and previously fetched refs/remotes/origin/foo
-                    yield git.branchDelete(true, branch);
+                if (ref) {
+                    ref = ref.startsWith('refs/') ? ref : `refs/heads/${ref}`;
+                    if (ref.startsWith('refs/heads/')) {
+                        const upperName1 = ref.toUpperCase().substr('REFS/HEADS/'.length);
+                        const upperName1Slash = `${upperName1}/`;
+                        branches = yield git.branchList(true);
+                        for (const branch of branches) {
+                            const upperName2 = branch.substr('origin/'.length).toUpperCase();
+                            const upperName2Slash = `${upperName2}/`;
+                            if (upperName1.startsWith(upperName2Slash) ||
+                                upperName2.startsWith(upperName1Slash)) {
+                                yield git.branchDelete(true, branch);
+                            }
+                        }
+                    }
                 }
                 core.endGroup();
                 // Clean
@@ -9336,6 +9563,11 @@ const v4_1 = __importDefault(__webpack_require__(826));
 const IS_WINDOWS = process.platform === 'win32';
 function downloadRepository(authToken, owner, repo, ref, commit, repositoryPath) {
     return __awaiter(this, void 0, void 0, function* () {
+        // Determine the default branch
+        if (!ref && !commit) {
+            core.info('Determining the default branch');
+            ref = yield getDefaultBranch(authToken, owner, repo);
+        }
         // Download the archive
         let archiveData = yield retryHelper.execute(() => __awaiter(this, void 0, void 0, function* () {
             core.info('Downloading the archive');
@@ -9380,6 +9612,42 @@ function downloadRepository(authToken, owner, repo, ref, commit, repositoryPath)
     });
 }
 exports.downloadRepository = downloadRepository;
+/**
+ * Looks up the default branch name
+ */
+function getDefaultBranch(authToken, owner, repo) {
+    return __awaiter(this, void 0, void 0, function* () {
+        return yield retryHelper.execute(() => __awaiter(this, void 0, void 0, function* () {
+            core.info('Retrieving the default branch name');
+            const octokit = new github.GitHub(authToken);
+            let result;
+            try {
+                // Get the default branch from the repo info
+                const response = yield octokit.repos.get({ owner, repo });
+                result = response.data.default_branch;
+                assert.ok(result, 'default_branch cannot be empty');
+            }
+            catch (err) {
+                // Handle .wiki repo
+                if (err['status'] === 404 && repo.toUpperCase().endsWith('.WIKI')) {
+                    result = 'master';
+                }
+                // Otherwise error
+                else {
+                    throw err;
+                }
+            }
+            // Print the default branch
+            core.info(`Default branch '${result}'`);
+            // Prefix with 'refs/heads'
+            if (!result.startsWith('refs/')) {
+                result = `refs/heads/${result}`;
+            }
+            return result;
+        }));
+    });
+}
+exports.getDefaultBranch = getDefaultBranch;
 function downloadArchive(authToken, owner, repo, ref, commit) {
     return __awaiter(this, void 0, void 0, function* () {
         const octokit = new github.GitHub(authToken);
@@ -14282,9 +14550,6 @@ function getInputs() {
                 result.ref = `refs/heads/${result.ref}`;
             }
         }
-        if (!result.ref && !result.commit) {
-            result.ref = 'refs/heads/master';
-        }
     }
     // SHA?
     else if (result.ref.match(/^[0-9a-fA-F]{40}$/)) {
@@ -14319,7 +14584,7 @@ function getInputs() {
     core.debug(`submodules = ${result.submodules}`);
     core.debug(`recursive submodules = ${result.nestedSubmodules}`);
     // Auth token
-    result.authToken = core.getInput('token');
+    result.authToken = core.getInput('token', { required: true });
     // SSH
     result.sshKey = core.getInput('ssh-key');
     result.sshKnownHosts = core.getInput('ssh-known-hosts');

package.json

@@ -5,8 +5,8 @@
   "main": "lib/main.js",
   "scripts": {
     "build": "tsc && ncc build && node lib/misc/generate-docs.js",
-    "format": "prettier --write **/*.ts",
+    "format": "prettier --write '**/*.ts'",
-    "format-check": "prettier --check **/*.ts",
+    "format-check": "prettier --check '**/*.ts'",
     "lint": "eslint src/**/*.ts",
     "test": "jest"
   },

src/git-command-manager.ts

@@ -3,6 +3,7 @@ import * as exec from '@actions/exec'
 import * as fshelper from './fs-helper'
 import * as io from '@actions/io'
 import * as path from 'path'
+import * as refHelper from './ref-helper'
 import * as regexpHelper from './regexp-helper'
 import * as retryHelper from './retry-helper'
 import {GitVersion} from './git-version'
@@ -23,16 +24,19 @@ export interface IGitCommandManager {
     globalConfig?: boolean
   ): Promise<void>
   configExists(configKey: string, globalConfig?: boolean): Promise<boolean>
-  fetch(fetchDepth: number, refSpec: string[]): Promise<void>
+  fetch(refSpec: string[], fetchDepth?: number): Promise<void>
+  getDefaultBranch(repositoryUrl: string): Promise<string>
   getWorkingDirectory(): string
   init(): Promise<void>
   isDetached(): Promise<boolean>
   lfsFetch(ref: string): Promise<void>
   lfsInstall(): Promise<void>
-  log1(): Promise<void>
+  log1(): Promise<string>
   remoteAdd(remoteName: string, remoteUrl: string): Promise<void>
   removeEnvironmentVariable(name: string): void
+  revParse(ref: string): Promise<string>
   setEnvironmentVariable(name: string, value: string): void
+  shaExists(sha: string): Promise<boolean>
   submoduleForeach(command: string, recursive: boolean): Promise<string>
   submoduleSync(recursive: boolean): Promise<void>
   submoduleUpdate(fetchDepth: number, recursive: boolean): Promise<void>
@@ -164,17 +168,14 @@ class GitCommandManager {
     return output.exitCode === 0
   }
 
-  async fetch(fetchDepth: number, refSpec: string[]): Promise<void> {
+  async fetch(refSpec: string[], fetchDepth?: number): Promise<void> {
-    const args = [
+    const args = ['-c', 'protocol.version=2', 'fetch']
-      '-c',
+    if (!refSpec.some(x => x === refHelper.tagsRefSpec)) {
-      'protocol.version=2',
+      args.push('--no-tags')
-      'fetch',
+    }
-      '--no-tags',
+
-      '--prune',
+    args.push('--prune', '--progress', '--no-recurse-submodules')
-      '--progress',
+    if (fetchDepth && fetchDepth > 0) {
-      '--no-recurse-submodules'
-    ]
-    if (fetchDepth > 0) {
       args.push(`--depth=${fetchDepth}`)
     } else if (
       fshelper.fileExistsSync(
@@ -195,6 +196,34 @@ class GitCommandManager {
     })
   }
 
+  async getDefaultBranch(repositoryUrl: string): Promise<string> {
+    let output: GitOutput | undefined
+    await retryHelper.execute(async () => {
+      output = await this.execGit([
+        'ls-remote',
+        '--quiet',
+        '--exit-code',
+        '--symref',
+        repositoryUrl,
+        'HEAD'
+      ])
+    })
+
+    if (output) {
+      // Satisfy compiler, will always be set
+      for (let line of output.stdout.trim().split('\n')) {
+        line = line.trim()
+        if (line.startsWith('ref:') || line.endsWith('HEAD')) {
+          return line
+            .substr('ref:'.length, line.length - 'ref:'.length - 'HEAD'.length)
+            .trim()
+        }
+      }
+    }
+
+    throw new Error('Unexpected output when retrieving default branch')
+  }
+
   getWorkingDirectory(): string {
     return this.workingDirectory
   }
@@ -225,8 +254,9 @@ class GitCommandManager {
     await this.execGit(['lfs', 'install', '--local'])
   }
 
-  async log1(): Promise<void> {
+  async log1(): Promise<string> {
-    await this.execGit(['log', '-1'])
+    const output = await this.execGit(['log', '-1'])
+    return output.stdout
   }
 
   async remoteAdd(remoteName: string, remoteUrl: string): Promise<void> {
@@ -237,10 +267,27 @@ class GitCommandManager {
     delete this.gitEnv[name]
   }
 
+  /**
+   * Resolves a ref to a SHA. For a branch or lightweight tag, the commit SHA is returned.
+   * For an annotated tag, the tag SHA is returned.
+   * @param {string} ref  For example: 'refs/heads/master' or '/refs/tags/v1'
+   * @returns {Promise<string>}
+   */
+  async revParse(ref: string): Promise<string> {
+    const output = await this.execGit(['rev-parse', ref])
+    return output.stdout.trim()
+  }
+
   setEnvironmentVariable(name: string, value: string): void {
     this.gitEnv[name] = value
   }
 
+  async shaExists(sha: string): Promise<boolean> {
+    const args = ['rev-parse', '--verify', '--quiet', `${sha}^{object}`]
+    const output = await this.execGit(args, true)
+    return output.exitCode === 0
+  }
+
   async submoduleForeach(command: string, recursive: boolean): Promise<string> {
     const args = ['submodule', 'foreach']
     if (recursive) {

src/git-directory-helper.ts

@@ -5,13 +5,13 @@ import * as fsHelper from './fs-helper'
 import * as io from '@actions/io'
 import * as path from 'path'
 import {IGitCommandManager} from './git-command-manager'
-import {IGitSourceSettings} from './git-source-settings'
 
 export async function prepareExistingDirectory(
   git: IGitCommandManager | undefined,
   repositoryPath: string,
   repositoryUrl: string,
-  clean: boolean
+  clean: boolean,
+  ref: string
 ): Promise<void> {
   assert.ok(repositoryPath, 'Expected repositoryPath to be defined')
   assert.ok(repositoryUrl, 'Expected repositoryUrl to be defined')
@@ -56,10 +56,26 @@ export async function prepareExistingDirectory(
         await git.branchDelete(false, branch)
       }
 
-      // Remove all refs/remotes/origin/* to avoid conflicts
+      // Remove any conflicting refs/remotes/origin/*
-      branches = await git.branchList(true)
+      // Example 1: Consider ref is refs/heads/foo and previously fetched refs/remotes/origin/foo/bar
-      for (const branch of branches) {
+      // Example 2: Consider ref is refs/heads/foo/bar and previously fetched refs/remotes/origin/foo
-        await git.branchDelete(true, branch)
+      if (ref) {
+        ref = ref.startsWith('refs/') ? ref : `refs/heads/${ref}`
+        if (ref.startsWith('refs/heads/')) {
+          const upperName1 = ref.toUpperCase().substr('REFS/HEADS/'.length)
+          const upperName1Slash = `${upperName1}/`
+          branches = await git.branchList(true)
+          for (const branch of branches) {
+            const upperName2 = branch.substr('origin/'.length).toUpperCase()
+            const upperName2Slash = `${upperName2}/`
+            if (
+              upperName1.startsWith(upperName2Slash) ||
+              upperName2.startsWith(upperName1Slash)
+            ) {
+              await git.branchDelete(true, branch)
+            }
+          }
+        }
       }
       core.endGroup()
 

src/git-source-provider.ts

@@ -42,7 +42,8 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
       git,
       settings.repositoryPath,
       repositoryUrl,
-      settings.clean
+      settings.clean,
+      settings.ref
     )
   }
 
@@ -102,6 +103,21 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
     await authHelper.configureAuth()
     core.endGroup()
 
+    // Determine the default branch
+    if (!settings.ref && !settings.commit) {
+      core.startGroup('Determining the default branch')
+      if (settings.sshKey) {
+        settings.ref = await git.getDefaultBranch(repositoryUrl)
+      } else {
+        settings.ref = await githubApiHelper.getDefaultBranch(
+          settings.authToken,
+          settings.repositoryOwner,
+          settings.repositoryName
+        )
+      }
+      core.endGroup()
+    }
+
     // LFS install
     if (settings.lfs) {
       await git.lfsInstall()
@@ -109,8 +125,24 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
 
     // Fetch
     core.startGroup('Fetching the repository')
-    const refSpec = refHelper.getRefSpec(settings.ref, settings.commit)
+    if (settings.fetchDepth <= 0) {
-    await git.fetch(settings.fetchDepth, refSpec)
+      // Fetch all branches and tags
+      let refSpec = refHelper.getRefSpecForAllHistory(
+        settings.ref,
+        settings.commit
+      )
+      await git.fetch(refSpec)
+
+      // When all history is fetched, the ref we're interested in may have moved to a different
+      // commit (push or force push). If so, fetch again with a targeted refspec.
+      if (!(await refHelper.testRef(git, settings.ref, settings.commit))) {
+        refSpec = refHelper.getRefSpec(settings.ref, settings.commit)
+        await git.fetch(refSpec)
+      }
+    } else {
+      const refSpec = refHelper.getRefSpec(settings.ref, settings.commit)
+      await git.fetch(refSpec, settings.fetchDepth)
+    }
     core.endGroup()
 
     // Checkout info
@@ -170,7 +202,17 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
     }
 
     // Dump some info about the checked out commit
-    await git.log1()
+    const commitInfo = await git.log1()
+
+    // Check for incorrect pull request merge commit
+    await refHelper.checkCommitInfo(
+      settings.authToken,
+      commitInfo,
+      settings.repositoryOwner,
+      settings.repositoryName,
+      settings.ref,
+      settings.commit
+    )
   } finally {
     // Remove auth
     if (!settings.persistCredentials) {

src/github-api-helper.ts

@@ -19,6 +19,12 @@ export async function downloadRepository(
   commit: string,
   repositoryPath: string
 ): Promise<void> {
+  // Determine the default branch
+  if (!ref && !commit) {
+    core.info('Determining the default branch')
+    ref = await getDefaultBranch(authToken, owner, repo)
+  }
+
   // Download the archive
   let archiveData = await retryHelper.execute(async () => {
     core.info('Downloading the archive')
@@ -67,6 +73,46 @@ export async function downloadRepository(
   io.rmRF(extractPath)
 }
 
+/**
+ * Looks up the default branch name
+ */
+export async function getDefaultBranch(
+  authToken: string,
+  owner: string,
+  repo: string
+): Promise<string> {
+  return await retryHelper.execute(async () => {
+    core.info('Retrieving the default branch name')
+    const octokit = new github.GitHub(authToken)
+    let result: string
+    try {
+      // Get the default branch from the repo info
+      const response = await octokit.repos.get({owner, repo})
+      result = response.data.default_branch
+      assert.ok(result, 'default_branch cannot be empty')
+    } catch (err) {
+      // Handle .wiki repo
+      if (err['status'] === 404 && repo.toUpperCase().endsWith('.WIKI')) {
+        result = 'master'
+      }
+      // Otherwise error
+      else {
+        throw err
+      }
+    }
+
+    // Print the default branch
+    core.info(`Default branch '${result}'`)
+
+    // Prefix with 'refs/heads'
+    if (!result.startsWith('refs/')) {
+      result = `refs/heads/${result}`
+    }
+
+    return result
+  })
+}
+
 async function downloadArchive(
   authToken: string,
   owner: string,

src/input-helper.ts

@@ -68,10 +68,6 @@ export function getInputs(): IGitSourceSettings {
         result.ref = `refs/heads/${result.ref}`
       }
     }
-
-    if (!result.ref && !result.commit) {
-      result.ref = 'refs/heads/master'
-    }
   }
   // SHA?
   else if (result.ref.match(/^[0-9a-fA-F]{40}$/)) {
@@ -110,7 +106,7 @@ export function getInputs(): IGitSourceSettings {
   core.debug(`recursive submodules = ${result.nestedSubmodules}`)
 
   // Auth token
-  result.authToken = core.getInput('token')
+  result.authToken = core.getInput('token', {required: true})
 
   // SSH
   result.sshKey = core.getInput('ssh-key')

src/ref-helper.ts

@@ -1,4 +1,9 @@
+import {URL} from 'url'
 import {IGitCommandManager} from './git-command-manager'
+import * as core from '@actions/core'
+import * as github from '@actions/github'
+
+export const tagsRefSpec = '+refs/tags/*:refs/tags/*'
 
 export interface ICheckoutInfo {
   ref: string
@@ -57,6 +62,16 @@ export async function getCheckoutInfo(
   return result
 }
 
+export function getRefSpecForAllHistory(ref: string, commit: string): string[] {
+  const result = ['+refs/heads/*:refs/remotes/origin/*', tagsRefSpec]
+  if (ref && ref.toUpperCase().startsWith('REFS/PULL/')) {
+    const branch = ref.substring('refs/pull/'.length)
+    result.push(`+${commit || ref}:refs/remotes/pull/${branch}`)
+  }
+
+  return result
+}
+
 export function getRefSpec(ref: string, commit: string): string[] {
   if (!ref && !commit) {
     throw new Error('Args ref and commit cannot both be empty')
@@ -107,3 +122,162 @@ export function getRefSpec(ref: string, commit: string): string[] {
     return [`+${ref}:${ref}`]
   }
 }
+
+/**
+ * Tests whether the initial fetch created the ref at the expected commit
+ */
+export async function testRef(
+  git: IGitCommandManager,
+  ref: string,
+  commit: string
+): Promise<boolean> {
+  if (!git) {
+    throw new Error('Arg git cannot be empty')
+  }
+
+  if (!ref && !commit) {
+    throw new Error('Args ref and commit cannot both be empty')
+  }
+
+  // No SHA? Nothing to test
+  if (!commit) {
+    return true
+  }
+  // SHA only?
+  else if (!ref) {
+    return await git.shaExists(commit)
+  }
+
+  const upperRef = ref.toUpperCase()
+
+  // refs/heads/
+  if (upperRef.startsWith('REFS/HEADS/')) {
+    const branch = ref.substring('refs/heads/'.length)
+    return (
+      (await git.branchExists(true, `origin/${branch}`)) &&
+      commit === (await git.revParse(`refs/remotes/origin/${branch}`))
+    )
+  }
+  // refs/pull/
+  else if (upperRef.startsWith('REFS/PULL/')) {
+    // Assume matches because fetched using the commit
+    return true
+  }
+  // refs/tags/
+  else if (upperRef.startsWith('REFS/TAGS/')) {
+    const tagName = ref.substring('refs/tags/'.length)
+    return (
+      (await git.tagExists(tagName)) && commit === (await git.revParse(ref))
+    )
+  }
+  // Unexpected
+  else {
+    core.debug(`Unexpected ref format '${ref}' when testing ref info`)
+    return true
+  }
+}
+
+export async function checkCommitInfo(
+  token: string,
+  commitInfo: string,
+  repositoryOwner: string,
+  repositoryName: string,
+  ref: string,
+  commit: string
+): Promise<void> {
+  try {
+    // GHES?
+    if (isGhes()) {
+      return
+    }
+
+    // Auth token?
+    if (!token) {
+      return
+    }
+
+    // Public PR synchronize, for workflow repo?
+    if (
+      fromPayload('repository.private') !== false ||
+      github.context.eventName !== 'pull_request' ||
+      fromPayload('action') !== 'synchronize' ||
+      repositoryOwner !== github.context.repo.owner ||
+      repositoryName !== github.context.repo.repo ||
+      ref !== github.context.ref ||
+      !ref.startsWith('refs/pull/') ||
+      commit !== github.context.sha
+    ) {
+      return
+    }
+
+    // Head SHA
+    const expectedHeadSha = fromPayload('after')
+    if (!expectedHeadSha) {
+      core.debug('Unable to determine head sha')
+      return
+    }
+
+    // Base SHA
+    const expectedBaseSha = fromPayload('pull_request.base.sha')
+    if (!expectedBaseSha) {
+      core.debug('Unable to determine base sha')
+      return
+    }
+
+    // Expected message?
+    const expectedMessage = `Merge ${expectedHeadSha} into ${expectedBaseSha}`
+    if (commitInfo.indexOf(expectedMessage) >= 0) {
+      return
+    }
+
+    // Extract details from message
+    const match = commitInfo.match(/Merge ([0-9a-f]{40}) into ([0-9a-f]{40})/)
+    if (!match) {
+      core.debug('Unexpected message format')
+      return
+    }
+
+    // Post telemetry
+    const actualHeadSha = match[1]
+    if (actualHeadSha !== expectedHeadSha) {
+      core.debug(
+        `Expected head sha ${expectedHeadSha}; actual head sha ${actualHeadSha}`
+      )
+      const octokit = new github.GitHub(token, {
+        userAgent: `actions-checkout-tracepoint/1.0 (code=STALE_MERGE;owner=${repositoryOwner};repo=${repositoryName};pr=${fromPayload(
+          'number'
+        )};run_id=${
+          process.env['GITHUB_RUN_ID']
+        };expected_head_sha=${expectedHeadSha};actual_head_sha=${actualHeadSha})`
+      })
+      await octokit.repos.get({owner: repositoryOwner, repo: repositoryName})
+    }
+  } catch (err) {
+    core.debug(`Error when validating commit info: ${err.stack}`)
+  }
+}
+
+function fromPayload(path: string): any {
+  return select(github.context.payload, path)
+}
+
+function select(obj: any, path: string): any {
+  if (!obj) {
+    return undefined
+  }
+
+  const i = path.indexOf('.')
+  if (i < 0) {
+    return obj[path]
+  }
+
+  const key = path.substr(0, i)
+  return select(obj[key], path.substr(i + 1))
+}
+
+function isGhes(): boolean {
+  const ghUrl = new URL(
+    process.env['GITHUB_SERVER_URL'] || 'https://github.com'
+  )
+  return ghUrl.hostname.toUpperCase() !== 'GITHUB.COM'
+}