Update to sbt 2.0.0 and cross-publish plugin for sbt 1.x and 2.x

[rolang]

Summary

Upgrade the build to sbt 2.0.0 and configure the sbt plugin module to cross-publish for both sbt 1.x and sbt 2.x.

Changes

• sbt version: project/build.properties updated to sbt.version=2.0.0
• Cross-building: The plugin module now cross-builds for Scala 2.12 (sbt 1.12.11) and Scala 3.8.4 (sbt 2.0.0) via pluginCrossBuild / sbtVersion mapping
• Version-specific sources:
  • src/main/scala-2.12/ — sbt 1 settings with Ivy-based resolver, csrConfiguration, in syntax
  • src/main/scala-3/ — sbt 2 settings with / syntax, no Ivy dependency, relies on Java URL handler for artifactregistry://
• Core module: Now cross-compiles for Scala 3.8.4 as well (needed by sbt 2 plugin)
• Removed: project/update.sbt (sbt-dependency-updates not available for sbt 2), project/metals.sbt (auto-generated, incompatible plugins)
• Deprecated: sbt-sonatype plugin is no longer needed — sbt 2 has native Sonatype support (localStaging, sonaRelease)

Plugin artifacts

Two plugin artifact variants are published:

• sbt-gar-handler_2.12_1.0 — for sbt 1.x
• sbt-gar-handler_sbt2_3 — for sbt 2.x

Test plan

• Verified sbt +compile cross-compiles all modules for all target Scala versions (2.12, 2.13, 3.8)
• Verified sbt +Test/compile cross-compiles tests
• Individual project compilation: core/compile, coursier/compile, plugin/compile all pass

[Copilot]

Pull request overview

This pull request upgrades the build to sbt 2.0.0 and updates the sbt plugin module so it can be published for both sbt 1.x (Scala 2.12) and sbt 2.x (Scala 3), with version-specific plugin implementation code split across Scala-versioned source directories.

Changes:

• Bumped sbt to 2.0.0 and updated the build to cross-compile the core module for Scala 2.12/2.13/3.
• Refactored the sbt plugin to delegate settings to a GarCompat implementation, split into Scala 2.12 (sbt 1) vs Scala 3 (sbt 2) source trees.
• Added an Ivy-based Artifact Registry resolver/repository implementation for the sbt 1.x plugin variant.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
project/build.properties	Updates the build to run on sbt 2.0.0.
build.sbt	Adds Scala 3 cross-compilation and configures plugin cross-publishing for sbt 1 vs sbt 2.
modules/sbt/src/main/scala/dev/rolang/sbt/gar/GarPlugin.scala	Delegates plugin settings to a version-specific compatibility layer.
modules/sbt/src/main/scala-3/dev/rolang/sbt/gar/GarCompat.scala	sbt 2 / Scala 3 compatibility settings relying on JVM URL handler installation.
modules/sbt/src/main/scala-2.12/dev/rolang/sbt/gar/GarCompat.scala	sbt 1 / Scala 2.12 compatibility settings, including coursier protocol handler deps + Ivy resolver mapping.
modules/sbt/src/main/scala-2.12/dev/rolang/sbt/gar/ArtifactRegistryIvyRepository.scala	New Ivy repository/resolver implementation for Artifact Registry publishing/resolution on sbt 1.x.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.