Add export command documentation

modules/cli/src/main/scala/scala/cli/commands/export0/ExportOptions.scala

@@ -54,7 +54,8 @@ object ExportOptions {
   implicit lazy val parser: Parser[ExportOptions] = Parser.derive
   implicit lazy val help: Help[ExportOptions]     = Help.derive
 
-  private val helpHeader = "Export current project to an external build tool (like SBT or Mill)."
+  private val helpHeader =
+    "Export current project to an external build tool (like SBT or Mill) or to JSON."
   val helpMessage: String =
     s"""$helpHeader
        |

modules/cli/src/main/scala/scala/cli/commands/shared/SharedOptions.scala

@@ -46,7 +46,7 @@ import scala.util.Properties
 import scala.util.control.NonFatal
 
 // format: off
-final case class SharedOptions(
+final case class  SharedOptions(
   @Recurse
     suppress: SuppressWarningOptions = SuppressWarningOptions(),
   @Recurse

website/docs/commands/export.md

@@ -0,0 +1,151 @@
+---
+title: Export ⚡️
+sidebar_position: 27
+---
+
+Export outputs information about current project to a format used by external build tools such as SBT or Mill.
+Additionally the command supports JSON format for custom analysis of projects.
+
+The project configuration is read both from information specified in source files
+as well as options passed to the `export` command
+
+Let's take a simple one-file project as an example:
+```scala title=Hello.scala
+//> using scala "3.1.3"
+//> using option "-Xasync"
+//> using dep "com.lihaoyi::os-lib:0.9.0"
+
+object Hello {
+  def main(args: Array[String]): Unit =
+    println(os.pwd)
+}
+```
+
+# Exporting to SBT:
+
+```bash ignore
+scala-cli export Hello.scala --sbt
+```
+Note that `--sbt` is not required here since it's the default.
+
+The result is a sbt-compliant project created in the `dest/` directory:
+
+```
+dest
+├── project
+│   └── build.properties
+├── src
+│   └── main
+│       └── scala
+│           └── Hello.scala
+└── build.sbt
+```
+
+All the project's configuration resides now in `dest/build.sbt`:
+
+
+```scala title=dest/build.sbt
+scalaVersion := "3.1.3"
+
+scalacOptions ++= Seq("-Xasync")
+
+libraryDependencies += "com.lihaoyi" %% "os-lib" % "0.9.0" 
+
+libraryDependencies += "com.lihaoyi" %% "os-lib" % "0.9.0" % Test
+
+```
+
+
+To further configure the new SBT project you can pass options to the `export` command:
+- `setting` - extra SBT settings like XXXXX
+- `sbtVersion` - version of SBT used for the export, default is 1.6.1
+
+
+# Exporting to Mill:
+
+```bash ignore
+scala-cli export Hello.scala --mill
+```
+Now the `--mill` option is required.
+
+The results are again created in the `dest/` directory:
+
+```
+dest
+├── project
+│   └── src
+│       └── Hello.scala
+├── .mill-version
+├── build.sc
+├── mill
+└── mill.bat
+```
+
+And all the project's configuration resides now in `dest/build.sc`:
+
+```scala title=dest/build.sc
+import mill._
+import mill.scalalib._
+object project extends ScalaModule {
+  def scalaVersion = "3.1.3"
+  def scalacOptions = super.scalacOptions() ++ Seq("-Xasync")
+  def ivyDeps = super.ivyDeps() ++ Seq(
+    ivy"com.lihaoyi::os-lib:0.9.0"
+  )
+
+  object test extends Tests {
+    def ivyDeps = super.ivyDeps() ++ Seq(
+      ivy"com.lihaoyi::os-lib:0.9.0"
+    )
+  }
+}
+
+```
+
+The script files `mill` and `mill.bat` are mill wrappers fetched from [lefou/millw repository](https://github.com/lefou/millw/tree/166bcdf5741de8569e0630e18c3b2ef7e252cd96).
+To change the build tool version used override the contents of `dest/.mill-version`, default is 0.10.10.
+
+
+# Exporting to JSON:
+
+For exporting information into a more readable format use the `--json` flag.
+
+```bash ignore
+scala-cli export Hello.scala --json
+```
+
+The result is the `dest/export.json` file:
+
+```json title=dest/export.json
+{
+ "scalaVersion": "3.1.3",
+ "platform": "JVM",
+ "scopes": {
+  "main": {
+   "sources": [
+    "Foo.scala"
+   ],
+   "scalacOptions": [
+    "-Xasync"
+   ],
+   "dependencies": [
+    {
+     "groupId": "com.lihaoyi",
+     "artifactId": {
+      "name": "os-lib",
+      "fullName": "os-lib_3"
+     },
+     "version": "0.9.0"
+    }
+   ],
+   "resolvers": [
+    "https://repo1.maven.org/maven2",
+    "ivy:file:///Users/mgajek/Library/Caches/ScalaCli/local-repo/v0.1.20-111-648755-DIRTY2ba64fdc//[organisation]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]",
+    "ivy:file:/Users/mgajek/.ivy2/local/[organisation]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]"
+   ]
+  }
+ }
+}
+```
+
+Note that the path to the output directory (`dest` by default) can be overriden with `output` option.

website/docs/reference/commands.md

@@ -54,7 +54,7 @@ Accepts option groups: [compilation server](./cli-options.md#compilation-server-
 
 ## export
 
-Export current project to an external build tool (like SBT or Mill).
+Export current project to an external build tool (like SBT or Mill) or to JSON.
 
 Detailed documentation can be found on our website: https://scala-cli.virtuslab.org