Support --reference to local repository

README.md

@@ -98,6 +98,11 @@ Please refer to the [release page](https://github.com/actions/checkout/releases/
     # Default: true
     show-progress: ''
 
+    # Path to a local bare git [reference repository to minimize network
+    # usage](https://git-scm.com/docs/git-clone#Documentation/git-clone.txt---reference-if-ableltrepositorygt).
+    # If the directory doesn't exists this option will ignore it and log a message.
+    reference: ''
+
     # Whether to download Git-LFS files
     # Default: false
     lfs: ''

__test__/git-auth-helper.test.ts

@@ -762,6 +762,7 @@ async function setup(testName: string): Promise<void> {
     lfsInstall: jest.fn(),
     log1: jest.fn(),
     remoteAdd: jest.fn(),
+    referenceAdd: jest.fn(),
     removeEnvironmentVariable: jest.fn((name: string) => delete git.env[name]),
     revParse: jest.fn(),
     setEnvironmentVariable: jest.fn((name: string, value: string) => {
@@ -821,7 +822,8 @@ async function setup(testName: string): Promise<void> {
     sshStrict: true,
     workflowOrganizationId: 123456,
     setSafeDirectory: true,
-    githubServerUrl: githubServerUrl
+    githubServerUrl: githubServerUrl,
+    reference: '/some/path'
   }
 }
 

__test__/git-directory-helper.test.ts

@@ -477,6 +477,7 @@ async function setup(testName: string): Promise<void> {
     lfsInstall: jest.fn(),
     log1: jest.fn(),
     remoteAdd: jest.fn(),
+    referenceAdd: jest.fn(),
     removeEnvironmentVariable: jest.fn(),
     revParse: jest.fn(),
     setEnvironmentVariable: jest.fn(),

__test__/input-helper.test.ts

@@ -91,6 +91,7 @@ describe('input-helper tests', () => {
     expect(settings.repositoryOwner).toBe('some-owner')
     expect(settings.repositoryPath).toBe(gitHubWorkspace)
     expect(settings.setSafeDirectory).toBe(true)
+    expect(settings.reference).toBe(undefined)
   })
 
   it('qualifies ref', async () => {

action.yml

@@ -76,6 +76,12 @@ inputs:
   show-progress:
     description: 'Whether to show progress status output when fetching.'
     default: true
+  reference:
+    required: false
+    description: >
+      Path to a local bare git [reference repository to minimize network usage](https://git-scm.com/docs/git-clone#Documentation/git-clone.txt---reference-if-ableltrepositorygt).
+
+      If the directory doesn't exists this option will ignore it and log a message.
   lfs:
     description: 'Whether to download Git-LFS files'
     default: false

dist/index.js

@@ -732,6 +732,13 @@ class GitCommandManager {
             yield this.execGit(['remote', 'add', remoteName, remoteUrl]);
         });
     }
+    referenceAdd(alternateObjects) {
+        return __awaiter(this, void 0, void 0, function* () {
+            const alternatePath = path.join(this.workingDirectory, '.git/objects/info/alternates');
+            core.info(`Adding a git alternate to reference repo at ${alternateObjects}`);
+            yield fs.promises.writeFile(alternatePath, `${alternateObjects}\n`);
+        });
+    }
     removeEnvironmentVariable(name) {
         delete this.gitEnv[name];
     }
@@ -1211,6 +1218,17 @@ function getSource(settings) {
                 yield git.init();
                 yield git.remoteAdd('origin', repositoryUrl);
                 core.endGroup();
+                if (settings.reference !== undefined) {
+                    const alternateObjects = path.join(settings.reference, '/objects');
+                    if (fsHelper.directoryExistsSync(alternateObjects, false)) {
+                        core.startGroup('Adding a reference repository');
+                        yield git.referenceAdd(alternateObjects);
+                        core.endGroup();
+                    }
+                    else {
+                        core.warning(`Reference repository was specified, but directory ${alternateObjects} does not exists`);
+                    }
+                }
             }
             // Disable automatic garbage collection
             core.startGroup('Disabling automatic garbage collection');
@@ -1790,6 +1808,8 @@ function getInputs() {
         // Determine the GitHub URL that the repository is being hosted from
         result.githubServerUrl = core.getInput('github-server-url');
         core.debug(`GitHub Host URL = ${result.githubServerUrl}`);
+        result.reference = core.getInput('reference');
+        core.debug(`Reference repository = ${result.reference}`);
         return result;
     });
 }

src/git-command-manager.ts

@@ -45,6 +45,7 @@ export interface IGitCommandManager {
   lfsInstall(): Promise<void>
   log1(format?: string): Promise<string>
   remoteAdd(remoteName: string, remoteUrl: string): Promise<void>
+  referenceAdd(reference: string): Promise<void>
   removeEnvironmentVariable(name: string): void
   revParse(ref: string): Promise<string>
   setEnvironmentVariable(name: string, value: string): void
@@ -353,6 +354,15 @@ class GitCommandManager {
     await this.execGit(['remote', 'add', remoteName, remoteUrl])
   }
 
+  async referenceAdd(alternateObjects: string): Promise<void> {
+    const alternatePath = path.join(
+      this.workingDirectory,
+      '.git/objects/info/alternates'
+    )
+    core.info(`Adding a git alternate to reference repo at ${alternateObjects}`)
+    await fs.promises.writeFile(alternatePath, `${alternateObjects}\n`)
+  }
+
   removeEnvironmentVariable(name: string): void {
     delete this.gitEnv[name]
   }

src/git-source-provider.ts

@@ -110,6 +110,18 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
       await git.init()
       await git.remoteAdd('origin', repositoryUrl)
       core.endGroup()
+
+      if (settings.reference !== undefined) {
+        const alternateObjects = path.join(settings.reference, '/objects')
+
+        if (fsHelper.directoryExistsSync(alternateObjects, false)) {
+          core.startGroup('Adding a reference repository')
+          await git.referenceAdd(alternateObjects)
+          core.endGroup()
+        } else {
+          core.warning(`Reference repository was specified, but directory ${alternateObjects} does not exists`);
+        }
+      }
     }
 
     // Disable automatic garbage collection

src/git-source-settings.ts

@@ -49,6 +49,11 @@ export interface IGitSourceSettings {
    */
   fetchDepth: number
 
+  /**
+   * The local reference repository
+   */
+  reference: string | undefined
+
   /**
    * Fetch tags, even if fetchDepth > 0 (default: false)
    */
@@ -59,6 +64,11 @@ export interface IGitSourceSettings {
    */
   showProgress: boolean
 
+  /**
+   * The local reference repository
+   */
+  reference: string | undefined
+
   /**
    * Indicates whether to fetch LFS objects
    */

src/input-helper.ts

@@ -159,5 +159,8 @@ export async function getInputs(): Promise<IGitSourceSettings> {
   result.githubServerUrl = core.getInput('github-server-url')
   core.debug(`GitHub Host URL = ${result.githubServerUrl}`)
 
+  result.reference = core.getInput('reference')
+  core.debug(`Reference repository = ${result.reference}`)
+
   return result
 }