Use JetBrains cache-redirector

CONTRIBUTING.md

@@ -78,6 +78,40 @@ plugins {
 
 There is an automation script for this routine, see [testDokka.sh.md](scripts/testDokka.sh.md) for details.
 
+### Updating Gradle
+
+To update Gradle, follow these steps:
+
+1. Open https://gradle.org/release-checksums/ and copy the "Binary-only (-bin) ZIP"
+   checksum corresponding to the desired Gradle version.
+2. Update `distributionSha256Sum` in [`gradle-wrapper.properties`](gradle/wrapper/gradle-wrapper.properties).
+    ```diff
+    - distributionSha256Sum=<old checksum>
+    + distributionSha256Sum=<new checksum>
+    ```
+3. Update `distributionSha256Sum` in the wrapper task in [`build.gradle.kts`](build.gradle.kts).
+    ```diff
+      tasks.wrapper {
+    -     distributionSha256Sum = "<old checksum>"
+    +     distributionSha256Sum = "<new checksum>"
+      }
+    ```
+   (Why does `distributionSha256Sum` need to be updated in two places? Because
+   [the Wrapper task fails if `gradle-wrapper.properties` contains `distributionSha256Sum`, but the task configuration does not.](https://docs.gradle.org/current/userguide/gradle_wrapper.html#configuring_checksum_verification))
+4. Update Gradle
+
+   Run `./gradlew wrapper --gradle-version=x.y.z`
+5. ⚠️ Important ⚠️
+
+   **Run** `./gradlew wrapper` **again**!
+
+   (Yes, really run `wrapper` twice. [Otherwise, Gradle won't update its wrapper files.](https://github.com/gradle/gradle/issues/884))
+6. Commit the
+   [`gradle/wrapper/**`](./gradle/wrapper),
+   [`gradlew`](gradlew),
+   and [`gradlew.bat`](gradlew.bat),
+   files to git (if there are changes).
+
 ### Updating public API dump
 
 [Binary Compatibility Validator](https://github.com/Kotlin/binary-compatibility-validator/blob/master/README.md) 

build.gradle.kts

@@ -93,23 +93,18 @@ fun includedBuildTasks(taskName: String, filter: (IncludedBuild) -> Boolean = {
 
 
 tasks.wrapper {
-    val gradleVersion = "8.7"
-    distributionUrl =
-        "https://cache-redirector.jetbrains.com/services.gradle.org/distributions/gradle-${gradleVersion}-bin.zip"
+    // Gradle requires that checksum is defined both in the wrapper task *and* in gradle-wrapper.properties
     // Checksums are available here: https://gradle.org/release-checksums/
     distributionSha256Sum = "544c35d6bd849ae8a5ed0bcea39ba677dc40f49df7d1835561582da2009b961d"
     doLast {
+        // Manually update the distribution URL to use cache-redirector.
+        // (Workaround for https://github.com/gradle/gradle/issues/17515)
         propertiesFile.writeText(
-            buildString {
-                appendLine("# DO NOT MODIFY THIS FILE")
-                appendLine("#")
-                appendLine("# To change the Gradle version modify the wrapper task in the root build.gradle.kts")
-                appendLine("#")
-                appendLine("# Explanation:")
-                appendLine("# Normally the easiest way to update Gradle is to edit gradle-wrapper.properties and re-run `gradle wrapper`.")
-                appendLine("# However, the wrapper task will overwrite the JetBrains cached URL unless it is specified in the task.")
-                append(propertiesFile.readText())
-            }
+            propertiesFile.readText()
+                .replace(
+                    "https\\://services.gradle.org/",
+                    "https\\://cache-redirector.jetbrains.com/services.gradle.org/",
+                )
         )
     }
 }

gradle/wrapper/gradle-wrapper.properties

@@ -1,10 +1,3 @@
-# DO NOT MODIFY THIS FILE
-#
-# To change the Gradle version modify the wrapper task in the root build.gradle.kts
-#
-# Explanation:
-# Normally the easiest way to update Gradle is to edit gradle-wrapper.properties and re-run `gradle wrapper`.
-# However, the wrapper task will overwrite the JetBrains cached URL unless it is specified in the task.
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 distributionSha256Sum=544c35d6bd849ae8a5ed0bcea39ba677dc40f49df7d1835561582da2009b961d