First complete plugin implementation.

build.sbt

@@ -8,7 +8,7 @@ externalResolvers := Seq(
 )
 
 val ProjectName: String = "sbt-gs-calver"
-val Description: String = "SBT 1.9.0+ plugin for Git-based semantic versioning."
+val Description: String = "SBT 1.9.0+ plugin for calendar versioning."
 
 def getProperty[A](
   name: String,

project/build.properties

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

src/main/scala/gs/CalVer.scala

@@ -1,6 +1,169 @@
 package gs
 
-case class CalVer(value: String)
+import java.time.LocalDate
+import scala.collection.mutable.ListBuffer
+
+/**
+  * Representation of a rendered Calendar Version.
+  *
+  * @param value The version string.
+  * @param pattern The pattern which rendered the version string.
+  */
+case class CalVer(
+  value: String,
+  pattern: CalVer.Pattern
+)
 
 object CalVer {
+  /**
+    * Render the given pattern to a Calendar Version.
+    *
+    * @param pattern The pattern to render.
+    * @return The rendered CalVer value.
+    */
+  def render(pattern: Pattern): CalVer = {
+    val today = LocalDate.now()
+    CalVer(
+      value = pattern.items.map {
+        case Left(component) => 
+          component match {
+            case Component.YYYY => today.getYear().toString()
+            case Component.MM => today.getMonthValue().toString()
+            case Component.DD => today.getDayOfMonth().toString()
+            case Component.Label(label) => label
+            case Component.GitSha(length) => Git.getSha(length)
+          }
+        case Right(delimiter) => Delimiter.render(delimiter)
+      }.mkString,
+      pattern = pattern
+    )
+  }
+
+  object Defaults {
+    /**
+      * Default pattern for release versions.
+      */
+    val ReleasePattern: Pattern = 
+      Pattern
+        .builder(Component.YYYY)
+        .addDelimiter(Delimiter.Dot)
+        .addComponent(Component.MM)
+        .addDelimiter(Delimiter.Dot)
+        .addComponent(Component.DD)
+        .addDelimiter(Delimiter.Hyphen)
+        .addComponent(Component.GitSha(7))
+        .build()
+
+    /**
+      * Default pattern for pre-release versions.
+      */
+    val PreReleasePattern: Pattern =
+      Pattern
+        .builder(Component.YYYY)
+        .addDelimiter(Delimiter.Dot)
+        .addComponent(Component.MM)
+        .addDelimiter(Delimiter.Dot)
+        .addComponent(Component.DD)
+        .addDelimiter(Delimiter.Hyphen)
+        .addComponent(Component.Label("SNAPSHOT"))
+        .build()
+  }
+
+  sealed trait Component
+
+  object Component {
+    /**
+      * CalVer Component: Year.
+      */
+    case object YYYY extends Component
+
+    /**
+      * CalVer Component: Month (1-12), without a leading zero.
+      */
+    case object MM extends Component
+
+    /**
+      * CalVer Component: Day of Month, without a leading zero.
+      */
+    case object DD extends Component
+
+    /**
+      * CalVer Component: Label.
+      *
+      * This component contains an arbitrary string value.
+      *
+      * @param value The value of the label.
+      */
+    case class Label(value: String) extends Component
+
+    /**
+      * CalVer Component. Git SHA.
+      *
+      * This component defines the length (first N characters) of the Git SHA to
+      * take from the current branch of the current repository. An empty string
+      * is used if lookup fails or no commits exist.
+      *
+      * @param length The number of characters of the Git SHA to use.
+      */
+    case class GitSha(length: Int) extends Component
+
+    def describe(component: Component): String = component match {
+      case YYYY => "YYYY"
+      case MM => "MM"
+      case DD => "DD"
+      case Label(value) => value
+      case GitSha(length) => s"SHA($length)"
+    }
+  }
+
+  sealed abstract class Delimiter(val value: String)
+
+  object Delimiter {
+    case object Dot extends Delimiter(".")
+    case object Hyphen extends Delimiter("-")
+    case object Plus extends Delimiter("+")
+    case object Underscore extends Delimiter("_")
+
+    def render(delimiter: Delimiter): String = delimiter.value
+  }
+
+  final class Pattern private (val items: List[Pattern.Item]) {
+    lazy val str: String = 
+      items.map {
+        case Left(component) => Component.describe(component)
+        case Right(delimiter) => Delimiter.render(delimiter)
+      }.mkString
+
+    override def toString(): String = str
+  }
+
+  object Pattern {
+    private type Item = Either[Component, Delimiter]
+
+    def builder(component: Component): Builder = Builder(component)
+
+    final class Builder private () {
+      private val buffer: ListBuffer[Item] = new ListBuffer()
+
+      def addComponent(component: Component): Builder = {
+        val _ = buffer.append(Left(component))
+        this
+      }
+
+      def addDelimiter(delimiter: Delimiter): Builder = {
+        val _ = buffer.append(Right(delimiter))
+        this
+      }
+
+      def build(): Pattern = new Pattern(buffer.toList)
+    }
+
+    object Builder {
+      def apply(component: Component): Builder = {
+        val b = new Builder()
+        b.addComponent(component)
+        b
+      }
+    }
+  }
 }

src/main/scala/gs/CalVerKeys.scala

@@ -12,6 +12,31 @@ object CalVerKeys {
     "Calculated CalVer."
   )
 
+  /**
+    * SBT setting which defines the CalVer pattern used to calculate the final
+    * version. This should not be set manually, please use 
+    * `calVerReleasePattern` and `calVerPreReleasePattern`.
+    */
+  lazy val calVerPattern = settingKey[CalVer.Pattern](
+    "Selected CalVer pattern."
+  )
+
+  /**
+    * User-defined SBT setting which defines the CalVer pattern to use for a
+    * release build.
+    */
+  lazy val calVerReleasePattern = settingKey[Option[CalVer.Pattern]](
+    "Pattern to use for calculating CalVer for release builds."
+  )
+
+  /**
+    * User-defined SBT setting which defines the CalVer pattern to use for a
+    * pre-release build.
+    */
+  lazy val calVerPreReleasePattern = settingKey[Option[CalVer.Pattern]](
+    "Pattern to use for calculating CalVer for pre-release builds."
+  )
+
   /** Task which emits the current version at the informational log level.
     */
   lazy val calVerInfo = taskKey[Unit](

src/main/scala/gs/CalVerPlugin.scala

@@ -11,9 +11,22 @@ object CalVerPlugin extends AutoPlugin {
 
   // Perform all version calculations and expose as a variable.
   lazy val calVerDefaults: Seq[Setting[_]] = {
-    // Expose the relevant values as setting keys.
+    val isRelease = PluginProperties.isRelease()
     Seq(
-      calVer := ""
+      calVerReleasePattern := calVerReleasePattern.value.orElse(
+        Some(CalVer.Defaults.ReleasePattern)
+      ), 
+      calVerPreReleasePattern := calVerPreReleasePattern.value.orElse(
+        Some(CalVer.Defaults.PreReleasePattern)
+      ),
+      calVerPattern := { 
+        if (isRelease) {
+          calVerReleasePattern.value.getOrElse(CalVer.Defaults.ReleasePattern)
+        } else {
+          calVerPreReleasePattern.value.getOrElse(CalVer.Defaults.PreReleasePattern)
+        }
+      } ,
+      calVer := CalVer.render(calVerPattern.value).value
     )
   }
 
@@ -25,6 +38,7 @@ object CalVerPlugin extends AutoPlugin {
     calVerInfo := {
       val log = Keys.streams.value.log
       log.info(s"[CalVer] Version: ${calVer.value}")
+      log.info(s"[CalVer] Pattern: ${calVerPattern.value}")
     }
   )
 

src/main/scala/gs/Git.scala

@@ -1,15 +1,16 @@
 package gs
 
-//import java.io.File
-//import scala.util.Try
-
 object Git {
-
+  /**
-  /*def getLatestSemVer(): SemVer = {
+    * Get the latest SHA. If there are no commits on this branch, the empty
-    // Suppress all error output. Suppress exceptions for the failed process.
+    * string will be returned.
-    // Capture the standard output and parse it if the command succeeds.
+    *
+    * @param length The number of characters to take from the SHA.
+    * @return The latest SHA.
+    */
+  def getSha(length: Int): String = {
     val result = os
-      .proc("git", "describe", "--tags", "--abbrev=0")
+      .proc("git", "rev-parse", "HEAD")
       .call(
         stderr = os.ProcessOutput(
           (
@@ -21,9 +22,8 @@ object Git {
       )
 
     if (result.exitCode != 0)
-      SemVer.DefaultVersion
+      result.out.text().take(length)
     else
-      SemVer.parse(result.out.text()).getOrElse(SemVer.DefaultVersion)
+      ""
-  }*/
+  }
-
 }

src/main/scala/gs/PluginProperties.scala

@@ -24,9 +24,8 @@ object PluginProperties {
 
     /** Use one of the following to calculate an incremented release version:
       *
-      *   - `sbt -Drelease=major`
+      *   - `sbt -Drelease=true`
-      *   - `sbt -Drelease=minor`
+      *   - `sbt -Drelease=false`
-      *   - `sbt -Drelease=patch`
       */
     val ReleaseProperty: String = "release"