Allow overriding upstream ref (#135113) (#135199)

For most devs the default of finding the elastic remote and the main
branch of that remote is the right upstream ref. But for tests that
operate on fake or local repositories it's useful to be able to override
the ref. This commit adds a parameter to the transport version resources
allowing to override the ref used to look at upstream.

build-tools-internal/src/integTest/groovy/org/elasticsearch/gradle/internal/transport/AbstractTransportVersionFuncTest.groovy

@@ -115,6 +115,9 @@ class AbstractTransportVersionFuncTest extends AbstractGradleFuncTest {
             include ':myserver'
             include ':myplugin'
         """
+        propertiesFile << """
+            org.elasticsearch.transports.upstreamRef=main
+        """
         versionPropertiesFile.text = versionPropertiesFile.text.replace("9.1.0", "9.2.0")
 
         file("myserver/build.gradle") << """

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/transport/TransportVersionResourcesPlugin.java

@@ -49,6 +49,10 @@ public class TransportVersionResourcesPlugin implements Plugin<Project> {
                 Directory transportResources = project.getLayout().getProjectDirectory().dir("src/main/resources/" + resourceRoot);
                 spec.getParameters().getTransportResourcesDirectory().set(transportResources);
                 spec.getParameters().getRootDirectory().set(project.getLayout().getSettingsDirectory().getAsFile());
+                Object upstreamRef = project.findProperty("org.elasticsearch.transport.upstreamRef");
+                if (upstreamRef != null) {
+                    spec.getParameters().getUpstreamRefOverride().set(upstreamRef.toString());
+                }
             });
 
         var depsHandler = project.getDependencies();

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/transport/TransportVersionResourcesService.java

@@ -12,8 +12,10 @@ package org.elasticsearch.gradle.internal.transport;
 import org.gradle.api.file.DirectoryProperty;
 import org.gradle.api.logging.Logger;
 import org.gradle.api.logging.Logging;
+import org.gradle.api.provider.Property;
 import org.gradle.api.services.BuildService;
 import org.gradle.api.services.BuildServiceParameters;
+import org.gradle.api.tasks.Optional;
 import org.gradle.process.ExecOperations;
 import org.gradle.process.ExecResult;
 
@@ -59,6 +61,9 @@ public abstract class TransportVersionResourcesService implements BuildService<T
         DirectoryProperty getTransportResourcesDirectory();
 
         DirectoryProperty getRootDirectory();
+
+        @Optional
+        Property<String> getUpstreamRefOverride();
     }
 
     @Inject
@@ -79,6 +84,9 @@ public abstract class TransportVersionResourcesService implements BuildService<T
     public TransportVersionResourcesService(Parameters params) {
         this.transportResourcesDir = params.getTransportResourcesDirectory().get().getAsFile().toPath();
         this.rootDir = params.getRootDirectory().get().getAsFile().toPath();
+        if (params.getUpstreamRefOverride().isPresent()) {
+            upstreamRefName.set(params.getUpstreamRefOverride().get());
+        }
     }
 
     /**