Allow configuring a Maven Central mirror via system property

Add support for a `mavenCentralMirror` system property that allows
users behind corporate proxies or firewalls to redirect all Maven
Central traffic through a mirror repository.

Users can configure this in `~/.gradle/gradle.properties`:
  systemProp.mavenCentralMirror=https://your-mirror.example.com

When unset, behavior is identical to today (uses mavenCentral()).

Co-authored-by: Isaac

Author: yzfeng2020

build.gradle

@@ -27,7 +27,12 @@ plugins {
 
 allprojects {
     repositories {
-        mavenCentral()
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        } else {
+            mavenCentral()
+        }
     }
 }
 

gradle/scripts/lib/common-dependencies.gradle

@@ -4,7 +4,12 @@ import org.yaml.snakeyaml.Yaml
 
 buildscript {
     repositories {
-        mavenCentral()
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        } else {
+            mavenCentral()
+        }
         gradlePluginPortal()
     }
 
@@ -33,10 +38,15 @@ configure(dependencyManagementProject) {
     apply plugin: 'java-platform'
 
     repositories {
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
         google()
         // Since we manage plugin versions here too.
         gradlePluginPortal()
-        mavenCentral()
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        } else {
+            mavenCentral()
+        }
     }
 
     javaPlatform {

gradle/scripts/lib/java-rpc-proto.gradle

@@ -2,6 +2,10 @@ import org.gradle.internal.os.OperatingSystem
 
 buildscript {
     repositories {
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        }
         gradlePluginPortal()
     }
     dependencies {

gradle/scripts/lib/java-shade.gradle

@@ -5,6 +5,10 @@ import java.util.concurrent.atomic.AtomicInteger
 
 buildscript {
     repositories {
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        }
         gradlePluginPortal()
         google()
     }

gradle/scripts/version-catalog.gradle

@@ -4,7 +4,12 @@ import org.tomlj.TomlArray
 
 buildscript {
     repositories {
-        mavenCentral()
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        } else {
+            mavenCentral()
+        }
     }
 
     dependencies {

settings.gradle

@@ -1,3 +1,13 @@
+pluginManagement {
+    repositories {
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        }
+        gradlePluginPortal()
+    }
+}
+
 plugins {
     // This plugin should be applied in settings.gradle, not build.gradle.
     // https://github.com/gradle/foojay-toolchains/issues/15

site-new/build.gradle

@@ -9,8 +9,13 @@ import java.util.stream.Collectors
 
 buildscript {
     repositories {
+        def mavenCentralMirror = System.getProperty('mavenCentralMirror')
+        if (mavenCentralMirror) {
+            maven { url = mavenCentralMirror }
+        } else {
+            mavenCentral()
+        }
         gradlePluginPortal()
-        mavenCentral()
     }
     dependencies {
         classpath libs.jsoup