sparse-checkout: optionally turn off cone mode

While it _is_ true that cone mode is the default nowadays (mainly for
performance reasons: code mode is much faster than non-cone mode), there
_are_ legitimate use cases where non-cone mode is really useful.

Let's add a flag to optionally disable cone mode.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

src/git-command-manager.ts

@@ -1,5 +1,6 @@
 import * as core from '@actions/core'
 import * as exec from '@actions/exec'
+import * as fs from 'fs'
 import * as fshelper from './fs-helper'
 import * as io from '@actions/io'
 import * as path from 'path'
@@ -17,6 +18,7 @@ export interface IGitCommandManager {
   branchExists(remote: boolean, pattern: string): Promise<boolean>
   branchList(remote: boolean): Promise<string[]>
   sparseCheckout(sparseCheckout: string[]): Promise<void>
+  sparseCheckoutNonConeMode(sparseCheckout: string[]): Promise<void>
   checkout(ref: string, startPoint: string): Promise<void>
   checkoutDetach(): Promise<void>
   config(
@@ -165,6 +167,23 @@ class GitCommandManager {
     await this.execGit(['sparse-checkout', 'set', ...sparseCheckout])
   }
 
+  async sparseCheckoutNonConeMode(sparseCheckout: string[]): Promise<void> {
+    await this.execGit(['config', 'core.sparseCheckout', 'true'])
+    const output = await this.execGit([
+      'rev-parse',
+      '--git-path',
+      'info/sparse-checkout'
+    ])
+    const sparseCheckoutPath = path.join(
+      this.workingDirectory,
+      output.stdout.trimRight()
+    )
+    await fs.promises.appendFile(
+      sparseCheckoutPath,
+      `\n${sparseCheckout.join('\n')}\n`
+    )
+  }
+
   async checkout(ref: string, startPoint: string): Promise<void> {
     const args = ['checkout', '--progress', '--force']
     if (startPoint) {

src/git-source-provider.ts

@@ -197,7 +197,11 @@ export async function getSource(settings: IGitSourceSettings): Promise<void> {
     // Sparse checkout
     if (settings.sparseCheckout) {
       core.startGroup('Setting up sparse checkout')
-      await git.sparseCheckout(settings.sparseCheckout)
+      if (settings.sparseCheckoutConeMode) {
+        await git.sparseCheckout(settings.sparseCheckout)
+      } else {
+        await git.sparseCheckoutNonConeMode(settings.sparseCheckout)
+      }
       core.endGroup()
     }
 

src/git-source-settings.ts

@@ -34,6 +34,11 @@ export interface IGitSourceSettings {
    */
   sparseCheckout: string[]
 
+  /**
+   * Indicates whether to use cone mode in the sparse checkout (if any)
+   */
+  sparseCheckoutConeMode: boolean
+
   /**
    * The depth when fetching
    */

src/input-helper.ts

@@ -89,6 +89,10 @@ export async function getInputs(): Promise<IGitSourceSettings> {
     core.debug(`sparse checkout = ${result.sparseCheckout}`)
   }
 
+  result.sparseCheckoutConeMode =
+    (core.getInput('sparse-checkout-cone-mode') || 'true').toUpperCase() ===
+    'TRUE'
+
   // Fetch depth
   result.fetchDepth = Math.floor(Number(core.getInput('fetch-depth') || '1'))
   if (isNaN(result.fetchDepth) || result.fetchDepth < 0) {