Allow the version to be emitted to file.

project/build.properties

@@ -1 +1 @@
-sbt.version=1.9.8
+sbt.version=1.9.9

src/main/scala/gs/SemVerKeys.scala

@@ -60,6 +60,13 @@ object SemVerKeys {
     "True or false depending on whether the current build is a pre-release (snapshot) build."
   )
 
+  /** SBT Setting that defines the filename for dumping the selected SemVer to a
+    * file.
+    */
+  lazy val semVerOutputFile = settingKey[Option[String]](
+    "Name of the file where the calculated SemVer will be stored (if requested)."
+  )
+
   /** Task which emits the current and selected versions at the informational
     * log level.
     */
@@ -67,4 +74,10 @@ object SemVerKeys {
     "Dump the calculated version information."
   )
 
+  /** Task which writes the selected SemVer to a file.
+    */
+  lazy val semVerWriteVersionToFile = taskKey[Unit](
+    "Write the selected SemVer to a file."
+  )
+
 }

src/main/scala/gs/SemVerPlugin.scala

@@ -1,5 +1,8 @@
 package gs
 
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.Paths
 import sbt._
 
 object SemVerPlugin extends AutoPlugin {
@@ -9,6 +12,8 @@ object SemVerPlugin extends AutoPlugin {
 
   import autoImport._
 
+  val DefaultOutputFile: String = ".version"
+
   // Perform all version calculations and expose as a variable.
   lazy val semVerDefaults: Seq[Setting[_]] = {
     // The latest semantic version relevant to this project, calculated by
@@ -43,10 +48,11 @@ object SemVerPlugin extends AutoPlugin {
 
     // Expose the relevant values as setting keys.
     Seq(
-      semVerCurrent  := latestSemVer.toString(),
-      semVerSelected := selectedSemVer.render(isSnapshot),
-      semVerMajor    := selectedSemVer.major,
-      semVerSnapshot := isSnapshot
+      semVerCurrent    := latestSemVer.toString(),
+      semVerSelected   := selectedSemVer.render(isSnapshot),
+      semVerMajor      := selectedSemVer.major,
+      semVerSnapshot   := isSnapshot,
+      semVerOutputFile := Some(DefaultOutputFile)
     )
   }
 
@@ -59,6 +65,13 @@ object SemVerPlugin extends AutoPlugin {
       val log = Keys.streams.value.log
       log.info(s"[SemVer] Current: ${semVerCurrent.value}")
       log.info(s"[SemVer] Selected: ${semVerSelected.value}")
+    },
+    semVerWriteVersionToFile := {
+      val outputFile = semVerOutputFile.value.getOrElse(DefaultOutputFile)
+      Files.write(
+        Paths.get(outputFile),
+        semVerSelected.value.getBytes(StandardCharsets.UTF_8)
+      )
     }
   )