try preserve local changes option

README.md

@@ -96,6 +96,11 @@ Please refer to the [release page](https://github.com/actions/checkout/releases/
     # Default: true
     clean: ''
 
+    # Whether to preserve local changes during checkout. If true, tries to preserve
+    # local files that are not tracked by Git. By default, all files will be overwritten.
+    # Default: false
+    preserveLocalChanges: ''
+
     # Partially clone against a given filter. Overrides sparse-checkout if set.
     # Default: null
     filter: ''
@@ -332,6 +337,21 @@ jobs:
 
 *NOTE:* The user email is `{user.id}+{user.login}@users.noreply.github.com`. See users API: https://api.github.com/users/github-actions%5Bbot%5D
 
+## Preserve local changes during checkout
+
+```yaml
+steps:
+  - name: Create file before checkout
+    shell: pwsh
+    run: New-Item -Path . -Name "example.txt" -ItemType "File"
+    
+  - name: Checkout with preserving local changes
+    uses: actions/checkout@v5
+    with:
+      clean: false
+      preserveLocalChanges: true
+```
+
 # Recommended permissions
 
 When using the `checkout` action in your GitHub Actions workflow, it is recommended to set the following `GITHUB_TOKEN` permissions to ensure proper functionality, unless alternative auth is provided via the `token` or `ssh-key` inputs:

action.yml

@@ -56,7 +56,10 @@ inputs:
     description: 'Relative path under $GITHUB_WORKSPACE to place the repository'
   clean:
     description: 'Whether to execute `git clean -ffdx && git reset --hard HEAD` before fetching'
-    default: true
+    default: 'true'
+  preserveLocalChanges:
+    description: 'Whether to preserve local changes during checkout. If true, tries to preserve local files that are not tracked by Git. By default, all files will be overwritten.'
+    default: 'false'
   filter:
     description: >
       Partially clone against a given filter.

src/git-command-manager.ts

@@ -22,7 +22,7 @@ export interface IGitCommandManager {
   disableSparseCheckout(): Promise<void>
   sparseCheckout(sparseCheckout: string[]): Promise<void>
   sparseCheckoutNonConeMode(sparseCheckout: string[]): Promise<void>
-  checkout(ref: string, startPoint: string): Promise<void>
+  checkout(ref: string, startPoint: string, options?: string[]): Promise<void>
   checkoutDetach(): Promise<void>
   config(
     configKey: string,
@@ -203,8 +203,21 @@ class GitCommandManager {
     )
   }
 
-  async checkout(ref: string, startPoint: string): Promise<void> {
-    const args = ['checkout', '--progress', '--force']
+  async checkout(
+    ref: string,
+    startPoint: string,
+    options: string[] = []
+  ): Promise<void> {
+    const args = ['checkout', '--progress']
+    
+    // Add custom options (like --merge) if provided
+    if (options.length > 0) {
+      args.push(...options)
+    } else {
+      // Default behavior - use force
+      args.push('--force')
+    }
+    
     if (startPoint) {
       args.push('-B', ref, startPoint)
     } else {

src/git-source-provider.ts

@@ -229,7 +229,15 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
 
     // Checkout
     core.startGroup('Checking out the ref')
+    if (settings.preserveLocalChanges) {
+      core.info('Attempting to preserve local changes during checkout')
+      // Use --merge to preserve local changes if possible
+      // This will fail if there are merge conflicts, but that's expected behavior
+      await git.checkout(checkoutInfo.ref, checkoutInfo.startPoint, ['--merge'])
+    } else {
+      // Use the default behavior with --force
       await git.checkout(checkoutInfo.ref, checkoutInfo.startPoint)
+    }
     core.endGroup()
 
     // Submodules

src/git-source-settings.ts

@@ -25,10 +25,15 @@ export interface IGitSourceSettings {
   commit: string
 
   /**
-   * Indicates whether to clean the repository
+   * Whether to execute git clean and git reset before fetching
    */
   clean: boolean
 
+  /**
+   * Whether to preserve local changes during checkout
+   */
+  preserveLocalChanges: boolean
+
   /**
    * The filter determining which objects to include
    */

src/input-helper.ts

@@ -82,6 +82,10 @@ export async function getInputs(): Promise<IGitSourceSettings> {
   result.clean = (core.getInput('clean') || 'true').toUpperCase() === 'TRUE'
   core.debug(`clean = ${result.clean}`)
 
+  // Preserve local changes
+  result.preserveLocalChanges = (core.getInput('preserveLocalChanges') || 'false').toUpperCase() === 'TRUE'
+  core.debug(`preserveLocalChanges = ${result.preserveLocalChanges}`)
+
   // Filter
   const filter = core.getInput('filter')
   if (filter) {