CliArgParser: allow additional values for --mode

scalafmt-cli/src/main/scala/org/scalafmt/cli/CliArgParser.scala

@@ -134,8 +134,8 @@ object CliArgParser {
         .text(
           s"""Sets the files to be formatted fetching mode.
             |Options:
-            |        diff - format files listed in `git diff` against master
-            |        changed - format files listed in `git status` (latest changes against previous commit)""".stripMargin
+            |${FileFetchMode.help}
+            |""".stripMargin
         )
       opt[String]("diff-branch")
         .action((branch, c) => c.copy(mode = Option(DiffFiles(branch))))

scalafmt-cli/src/main/scala/org/scalafmt/cli/FileFetchMode.scala

@@ -4,36 +4,59 @@ import scopt.Read
 
 /** Determines how we fetch files for formatting
   */
-sealed trait FileFetchMode
+sealed trait FileFetchMode {
+  def desc: String
+}
 
 object FileFetchMode {
 
+  private val available: Map[String, FileFetchMode] = Map(
+    "diff" -> DiffFiles("master"),
+    "changed" -> ChangedFiles,
+    "any" -> RecursiveSearch,
+    "anygit" -> GitFiles
+  )
+
+  def help = available
+    .map { case (k, v) => s"$k: ${v.desc}" }
+    .mkString("   ", "\n   ", "")
+
   /** The read instance is practically is not exhaustive due to the
     * RecursiveSearch and GitFiles are the fallback used in the absence of other
     * options
     */
-  implicit val read: Read[FileFetchMode] = Read.reads {
-    case "diff" => DiffFiles("master")
-    case "changed" => ChangedFiles
+  implicit val read: Read[FileFetchMode] = Read.reads { x =>
+    available
+      .getOrElse(x, throw new IllegalArgumentException(s"unknown mode: $x"))
   }
+
 }
 
 /** A simple recursive strategy where each directory is expanded
   */
-case object RecursiveSearch extends FileFetchMode
+case object RecursiveSearch extends FileFetchMode {
+  def desc: String = "format any files found in current directory"
+}
 
 /** A call to `git ls-files --name-only <dir>`
   */
-case object GitFiles extends FileFetchMode
+case object GitFiles extends FileFetchMode {
+  def desc: String = "format any git-tracked files found in current directory"
+}
 
 /** A call to `git diff --name-only --diff-filter=d <branch>`
   *
   * When this is set, files passed via the cli are ignored.
   */
-final case class DiffFiles(branch: String) extends FileFetchMode
+final case class DiffFiles(branch: String) extends FileFetchMode {
+  def desc: String = s"format files listed in `git diff` against $branch"
+}
 
 /** A call to `git status --porcelain`
   *
   * When this is set, files passed via the cli are ignored.
   */
-case object ChangedFiles extends FileFetchMode
+case object ChangedFiles extends FileFetchMode {
+  def desc: String =
+    "format files listed in `git status` (latest changes against previous commit)"
+}