Update the nightlies doc (#3213)

* Update the nightlies doc to mention repo.scala-lang.org

* Update _overviews/core/nightlies.md

Co-authored-by: Hamza Remmal <hamza@remmal.net>

---------

Co-authored-by: Hamza Remmal <hamza@remmal.net>

Author: Gedochao

_overviews/core/nightlies.md

@@ -8,80 +8,89 @@ We regularly publish nightly versions of both Scala 3 and 2 so that users can pr
 
 Here's how to find and use these versions.
 
-## Scala 3
+## General information on nightlies
 
-Scala 3 nightly versions are published to Maven Central. If you know the full version number of the nightly you want to use, you can use it just like any other Scala 3 version.
+### Scala 3
 
-One quick way to get that version number is to visit [https://dotty.epfl.ch](https://dotty.epfl.ch) and look in the upper left corner.
+Scala 3 nightly versions are published to [https://repo.scala-lang.org](https://repo.scala-lang.org). Historically, they used to be published to Maven Central. Old nightly versions of Scala 3 (all the way until `3.8.0-RC1-bin-20250822-658c8bd-NIGHTLY` in August 2025) are still available there, as well as via [https://repo.scala-lang.org](https://repo.scala-lang.org).
 
-Another way is to scrape Maven Central, as shown in this script: [https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc](https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc)
+If you know the full version number of the nightly you want to use, you can use it just like any other Scala 3 version.
 
-A third way is to use [scala-cli](https://scala-cli.virtuslab.org), as follows. (Since Scala 3.5.0, the `scala` command runs `scala-cli`.)
+There are a number of ways to get that version number, as listed below.
 
-### scala-cli
+### Scala 2
 
-You can run nightlies with commands such as:
-
-    scala-cli -S 3.nightly
-    scala-cli -S 3.3.nightly
-
-The default command is `repl`, but all the other scala-cli subcommands such as `compile` and `run` work, too. It also works with `//>` directives in your script itself, for example:
+We informally refer to Scala 2 “nightly” versions, but technically it's a misnomer. A so-called “nightly” is built for every merged PR in the Scala 2 repo.
 
-    //> using scala 3.nightly
-
-See this [scala-cli doc page](https://scala-cli.virtuslab.org/docs/commands/compile#scala-nightlies) for details.
+Similarly to Scala 3 nightlies, they are available at [https://repo.scala-lang.org](https://repo.scala-lang.org).
 
-## Scala 2.13 or 2.12
+## How to use nightly versions
 
-We informally refer to Scala 2 “nightly” versions, but technically it's a misnomer. A so-called “nightly” is built for every merged PR.
+### Scala CLI
 
-Scala 2 nightly versions are published to a special resolver. Unless you are using scala-cli, you'll need to add that resolver to your build configuration in order to use these versions.
+Scala CLI is the official runner of the language and has nightlies available without any extra configuration. From Scala 3.5.0 and on it's available under the `scala` command in Scala 3 installations. It can also be installed separately as `scala-cli`.
 
-### quick version (sbt)
+Note: The nightly repository is supported since Scala CLI v1.9.0 onwards (or `scala` installed with Scala 3.7.3 or newer).
 
-    Global / resolvers += "scala-integration" at
-      "https://scala-ci.typesafe.com/artifactory/scala-integration/"
-    scalaVersion := "2.13.15-bin-abcd123"
+You can run nightlies with commands such as:
 
-For a 2.12 nightly, substitute e.g. `2.12.20` for `2.13.15`; in either case, it's the version number of the _next_ release on that branch.
+    scala -e 'println("Hello") -S 3.nightly
+    scala -e 'println("Hello") -S 3.3.nightly
+    scala -e 'println("Hello") -S 2.13.nightly
+    scala -e 'println("Hello") -S 2.nightly # same as 2.13.nightly
+    scala -e 'println("Hello") -S 2.12.nightly
 
-For `abcd123`, substitute the first 7 characters of the SHA of the latest commit to the [2.13.x branch](https://github.com/scala/scala/commits/2.13.x) or [2.12.x branch](https://github.com/scala/scala/commits/2.12.x) that has a green checkmark. (Clicking the checkmark will show a CI job name with the whole version in its name.)
+The default command is `repl` (unless sources are passed, in which case it switches to `run`), but all the other scala-cli subcommands such as `compile` and `run` work, too. It also works with `//> using` directives in your script itself, for example:
 
-A quick way to find out the full version number of a current nightly is to use [scala-cli](https://scala-cli.virtuslab.org), as follows.
+    //> using scala 3.nightly
+    //> using scala 3.3.nightly
+    //> using scala 2.nightly
+    //> using scala 2.13.nightly
+    //> using scala 2.12.nightly
 
-### quick version (scala-cli)
+See this [scala-cli doc page](https://scala-cli.virtuslab.org/docs/commands/compile#scala-nightlies) for details.
 
-You can run nightlies with:
+### Get it from the nightly website
 
-    scala-cli -S 2.13.nightly
-    scala-cli -S 2.nightly     # same as 2.13.nightly
-    scala-cli -S 2.12.nightly
+A quick way to get that version number is to visit [https://nightly.scala-lang.org](https://nightly.scala-lang.org) and look in the upper left corner.
 
-The default command is `repl`, but all the other scala-cli subcommands such as `compile` and `run` work, too. It also works with `//>` directives in your script itself, for example:
+### Check the repository, directly
 
-    //> using scala 2.nightly
+Another way is to scrape the repository, as shown in this script: [https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc](https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc)
 
-### Longer explanation
+### SBT
 
-We no longer publish `-SNAPSHOT` versions of Scala 2.
+To use recent nightlies with SBT, adding the appropriate resolver to the build configuration is necessary.
 
-But the team does publish nightly versions, each with its own fixed version number. The version number of a nightly looks like e.g. `2.13.1-bin-abcd123`. (`-bin-` signals binary compatibility to sbt; all 2.13.x releases since 2.13.0 are binary compatible with each other.)
+    ThisBuild / scalaVersion := "3.8.0-RC1-bin-20250916-eb1bb73-NIGHTLY"
+    ThisBuild / resolvers += Resolver.scalaNightlyRepository
+    lazy val root = (project in file("."))
+      .settings(name := "sbt-with-scala-nightlies")
 
-To tell sbt to use one of these nightlies, you need to do three things.
+Also note that SBT 1.11.5 or newer is necessary.
 
-First, add the resolver where the nightlies are kept:
+### Mill
 
-    Global / resolvers += "scala-integration" at
-      "https://scala-ci.typesafe.com/artifactory/scala-integration/"
+To use recent nightlies with Mill, a custom resolver for the initial bootstrap of the build is needed. 
+Here's an example `build.mill` file:
 
-Second, specify the Scala version:
+    package build
+    import mill.*
+    import mill.api.*
+    import scalalib.*
 
-    scalaVersion := "2.13.1-bin-abcd123"
+    def scalaNightlyRepo = "https://repo.scala-lang.org/artifactory/maven-nightlies"
 
-But that isn't a real version number. Manually substitute a version number containing the 7-character SHA of the last commit in the [scala/scala repository](https://github.com/scala/scala) for which a nightly version was published.  Look at [https://travis-ci.org/scala/scala/branches](https://travis-ci.org/scala/scala/branches) and you'll see the SHA in the upper right corner of the 2.13.x (or 2.12.x) section.
+    object project extends ScalaModule {
+      def jvmWorker = ModuleRef(CustomJvmWorkerModule)
+      override def scalaVersion = "3.8.0-RC1-bin-20250916-eb1bb73-NIGHTLY"
+      override def repositories = Task { super.repositories() ++ Seq(scalaNightlyRepo)}
+    }
 
-As soon as 2.13.1 is released, the version number in the nightly will bump to 2.13.2, and so on.
+    object CustomJvmWorkerModule extends JvmWorkerModule, CoursierModule {
+      override def repositories = Task { super.repositories() ++ Seq(scalaNightlyRepo)}
+    }
 
-If you have a multiproject build, be sure you set these settings across all projects when you modify your build definition. Or, you may set them temporarily in the sbt shell with `++2.13.1-bin-abcd123` (sbt 0.13.x) or `++2.13.1-bin-abcd123!` (sbt 1.x; the added exclamation point is necessary to force a version not included in `crossScalaVersions` to be used).
+Note how the custom `JvmWorkerModule` is necessary with the added repository. It is not enough to just define it as a repository for the module dependencies.
 
-Ideally, we would suggest an automated way to ask Travis-CI for the right SHA. This is presumably possible via Travis-CI's API, but as far as we know, nobody has looked into it yet. (Is there a volunteer?)
+Also note that Mill 1.0.5 or newer is necessary for this.