Completed a fully functional plugin for SBT 1.9.0+.

build.sbt

@@ -1,4 +1,4 @@
-ThisBuild / version      := "0.1.0-SNAPSHOT"
+ThisBuild / organizationName := "garrity software"
 ThisBuild / organization     := "gs"
 
 ThisBuild / homepage := Some(
@@ -9,12 +9,71 @@ ThisBuild / licenses := Seq(
   "Apache-2.0" -> url("http://www.apache.org/license/LICENSE-2.0")
 )
 
-lazy val root = Project("gs-semver-sbt-plugin", file("."))
+externalResolvers := Seq(
+  "Garrity Software Releases" at "https://maven.garrity.co/releases"
+)
+
+val ProjectName: String = "gs-semver-sbt-plugin"
+val Description: String = "SBT 1.9.0+ plugin for Git-based semantic versioning."
+
+def getProperty[A](
+  name: String,
+  conv: String => A
+): Option[A] =
+  Option(System.getProperty(name)).map(conv)
+
+val VersionProperty: String = "version"
+val ReleaseProperty: String = "release"
+
+lazy val InputVersion: Option[String] =
+  getProperty(VersionProperty, identity)
+
+lazy val IsRelease: Boolean =
+  getProperty(ReleaseProperty, _.toBoolean).getOrElse(false)
+
+lazy val Modifier: String =
+  if (IsRelease) "" else "-SNAPSHOT"
+
+val DefaultVersion: String = "0.1.0-SNAPSHOT"
+
+lazy val SelectedVersion: String =
+  InputVersion
+    .map(v => s"$v$Modifier")
+    .getOrElse(DefaultVersion)
+
+lazy val publishSettings = Seq(
+  publishMavenStyle      := true,
+  Test / publishArtifact := false,
+  pomIncludeRepository   := Function.const(false),
+  scmInfo := Some(
+    ScmInfo(
+      url(s"https://git.garrity.co/garrity-software/$ProjectName"),
+      s"git@git.garrity.co:garrity-software/$ProjectName.git"
+    )
+  ),
+  description := Description,
+  licenses := List(
+    "Apache 2.0" -> url("https://www.apache.org/licenses/LICENSE-2.0.html")
+  ),
+  homepage := Some(
+    url(s"https://git.garrity.co/garrity-software/$ProjectName")
+  ),
+  publishTo := {
+    val repo = "https://maven.garrity.co/"
+    if (!IsRelease)
+      Some("Garrity Software Maven" at repo + "snapshots")
+    else
+      Some("Garrity Software Maven" at repo + "releases")
+  }
+)
+
+lazy val root = Project(ProjectName, file("."))
   .enablePlugins(SbtPlugin)
   .settings(
-    name := "gs-semver-sbt-plugin",
+    name    := ProjectName,
+    version := SelectedVersion,
     libraryDependencies ++= Seq(
-      "org.eclipse.jgit" % "org.eclipse.jgit" % "6.8.0.202311291450-r"
+      "com.lihaoyi" %% "os-lib" % "0.9.3"
     ),
     pluginCrossBuild / sbtVersion := {
       scalaBinaryVersion.value match {

src/main/scala/gs/Git.scala

@@ -1,38 +1,40 @@
 package gs
 
 import java.io.File
-import org.eclipse.jgit.lib.Constants
-import org.eclipse.jgit.lib.Repository
-import org.eclipse.jgit.revwalk.RevWalk
-import org.eclipse.jgit.storage.file.FileRepositoryBuilder
-import scala.collection.JavaConverters._
 import scala.util.Try
 
 object Git {
 
-  private lazy val repo: Repository = {
-    val builder = new FileRepositoryBuilder()
-    builder.setGitDir(new File(".")).findGitDir().build()
+  /** Get the latest tag on this repository and attempt to parse it as a
+    * [[SemVer]]. This value is retrieved using the `git` command. If for some
+    * reason the call fails, there are no tags, or the tag value cannot be
+    * parsed, the default [[SemVer]] (`0.1.0`) is used.
+    *
+    * This function assumes the current directory is a Git repository. The
+    * command executed is: `git describe --tags --abbrev=0`
+    *
+    * @return
+    *   The latest semantic version according to the current Git repository.
+    */
+  def getLatestSemVer(): SemVer = {
+    // Suppress all error output. Suppress exceptions for the failed process.
+    // Capture the standard output and parse it if the command succeeds.
+    val result = os
+      .proc("git", "describe", "--tags", "--abbrev=0")
+      .call(
+        stderr = os.ProcessOutput(
+          (
+            _,
+            _
+          ) => ()
+        ),
+        check = false
+      )
+
+    if (result.exitCode != 0)
+      SemVer.DefaultVersion
+    else
+      SemVer.parse(result.out.text()).getOrElse(SemVer.DefaultVersion)
   }
 
-  def getLatestSemVer(): Option[SemVer] = {
-    val walk = new RevWalk(repo)
-    val result = repo
-      .getRefDatabase()
-      .getRefsByPrefix(Constants.R_TAGS)
-      .asScala
-      .map(ref => walk.parseTag(ref.getObjectId()))
-      .sortBy(_.getTaggerIdent().getWhenAsInstant())
-      .headOption
-      .map(_.getTagName())
-      .map(normalizeTagName)
-      .flatMap(SemVer.parse)
-
-    walk.dispose()
-    result
-  }
-
-  private def normalizeTagName(tag: String): String =
-    tag.trim().stripPrefix("v")
-
 }

src/main/scala/gs/PluginProperties.scala

@@ -0,0 +1,65 @@
+package gs
+
+import sbt._
+
+/** Helper for managing all SBT command line properties (`-Dproperty=value`).
+  */
+object PluginProperties {
+
+  /** Helper to extract the value from `-Dproperty=value`.
+    *
+    * @param name
+    *   The property name.
+    * @param conv
+    *   The conversion function to the output type.
+    * @return
+    *   The converted value, or `None` if no value exists.
+    */
+  def getProperty[A](
+    name: String,
+    conv: String => A
+  ): Option[A] =
+    Option(System.getProperty(name)).map(conv)
+
+    /** Use one of the following to calculate an incremented release version:
+      *
+      *   - `sbt -Drelease=major`
+      *   - `sbt -Drelease=minor`
+      *   - `sbt -Drelease=patch`
+      */
+    val ReleaseProperty: String = "release"
+
+    /** If true, or no release type is set, this build is treated as a
+      * pre-release, and the suffix `-SNAPSHOT` is appended to the version.
+      */
+    val SnapshotProperty: String = "snapshot"
+
+    /** The value of `-Drelease=<value>`, parsed and validated. Influences the
+      * final calculated [[SemVer]].
+      *
+      * @return
+      *   The version passed as input to SBT.
+      */
+    def getReleaseType(): Option[ReleaseType] =
+      getProperty(
+        ReleaseProperty,
+        raw =>
+          ReleaseType.parse(raw) match {
+            case scala.util.Success(value) => value
+            case scala.util.Failure(e)     => throw e
+          }
+      )
+
+    /** The value of `-Dsnapshot=<value>`, parsed and validated. If parsing
+      * fails or no value is present, `false` is returned. Influences whether
+      * the pre-release suffix (`-SNAPSHOT`) is appended to the version.
+      *
+      * @return
+      *   `true` if `-Dsnapshot=true` is specified at the command line, `false`
+      *   otherwise.
+      */
+    def isSnapshot(): Boolean =
+      getProperty(SnapshotProperty, raw => raw.trim().equalsIgnoreCase("true"))
+        .getOrElse(false)
+
+}

src/main/scala/gs/ReleaseType.scala

@@ -0,0 +1,25 @@
+package gs
+
+import scala.util.Failure
+import scala.util.Success
+import scala.util.Try
+
+sealed abstract class ReleaseType(val name: String)
+
+object ReleaseType {
+  case object Major extends ReleaseType("major")
+  case object Minor extends ReleaseType("minor")
+  case object Patch extends ReleaseType("patch")
+
+  def parse(candidate: String): Try[ReleaseType] =
+    candidate.trim().toLowerCase() match {
+      case Major.name => Success(Major)
+      case Minor.name => Success(Minor)
+      case Patch.name => Success(Patch)
+      case _ =>
+        Failure(
+          new IllegalArgumentException(s"Invalid release type: '$candidate'")
+        )
+    }
+
+}

src/main/scala/gs/SemVer.scala

@@ -2,23 +2,76 @@ package gs
 
 import scala.util.matching.Regex
 
+/** Simplified representation of SemVer. Only supports major, minor and patch
+  * versions. Not intended to be used as a generalized SemVer implementation.
+  *
+  * @param major
+  *   The major version.
+  * @param minor
+  *   The minor version.
+  * @param patch
+  *   The patch version.
+  */
 case class SemVer(
   major: Int,
   minor: Int,
   patch: Int
 ) {
 
+  /** Render this SemVer as: `Major.Minor.Patch`
+    *
+    * @return
+    *   The `Major.Minor.Patch` representation of this SemVer.
+    */
   override def toString(): String =
     s"$major.$minor.$patch"
 
+  /** Render this SemVer as: `Major.Minor.Patch`, and append a suffix,
+    * `-SNAPSHOT` if a snapshot rendition is requested.
+    *
+    * @param isSnapshot
+    *   Requests a snapshot rendition if true. Uses the `-SNAPSHOT` pre-release
+    *   suffix.
+    * @return
+    *   The string rendition of this version.
+    */
+  def render(isSnapshot: Boolean): String = {
+    val version = toString()
+    if (isSnapshot) version + "-SNAPSHOT" else version
+  }
+
+  /** @return
+    *   Copy of this SemVer with the major version incremented by 1.
+    */
+  def incrementMajor(): SemVer = copy(major = this.major + 1)
+
+  /** @return
+    *   Copy of this SemVer with the minor version incremented by 1.
+    */
+  def incrementMinor(): SemVer = copy(minor = this.minor + 1)
+
+  /** @return
+    *   Copy of this SemVer with the patch version incremented by 1.
+    */
   def incrementPatch(): SemVer = copy(patch = this.patch + 1)
 }
 
 object SemVer {
 
-  val SemVerPattern: Regex =
+  /** Version 0.1.0
+    */
+  val DefaultVersion: SemVer = SemVer(0, 1, 0)
+
+  private val SemVerPattern: Regex =
     "^(0|(?:[1-9][0-9]*))\\.(0|(?:[1-9][0-9]*))\\.(0|(?:[1-9][0-9]*))$".r
 
+  /** Attempt to parse the input string as a [[SemVer]].
+    *
+    * @param candidate
+    *   The candidate string to parse.
+    * @return
+    *   The parsed [[SemVer]], or `None` if parsing failed.
+    */
   def parse(candidate: String): Option[SemVer] =
     candidate match {
       case SemVerPattern(major, minor, patch) =>

src/main/scala/gs/SemVerKeys.scala

@@ -2,26 +2,62 @@ package gs
 
 import sbt._
 
+/** Defines all setting and task keys for the GS SemVer SBT Plugin.
+  */
 object SemVerKeys {
 
-  /** SBT Setting Key for the latest known project version.
+  /** SBT Setting for the latest known project version (before this build).
+    *
+    * For setting your project version, please use the `semVerSelected` setting.
     *
     * This value is automatically derived from Git by looking at the most recent
     * tag. If the project does not yet have any tags, the value 0.1.0 is used.
     */
-  lazy val latestVersion = settingKey[String](
+  lazy val semVerCurrent = settingKey[String](
     "Latest Git-tagged project version, or 0.1.0 if no tags exist."
   )
 
-  /** SBT Setting Key for the working project version - used if there are any
-    * non-committed changes.
+  /** SBT Setting for the **selected** project version.
     *
-    * This value is automatically derived by taking the latest version, and
-    * either incrementing the revision by 1 or just using 0.1.0 if the project
-    * does not have any Git tags.
+    * Use this value to set your project version:
+    *
+    * {{{
+    * version := semVerSelected.value
+    * }}}
+    *
+    * This value should be used as the version for all project artifacts. It is
+    * automatically derived based on the `semVerCurrent` setting, the value of
+    * the `release` property, and the value of the `snapshot` property:
+    *
+    * Consider the example current version of `1.2.3`:
+    *
+    *   - `-Drelease=major`: `semVerSelected = 2.2.3`
+    *   - `-Drelease=major`, `-Dsnapshot=true`: `semVerSelected =
+    *     2.2.3-SNAPSHOT`
+    *   - `-Drelease=minor`: `semVerSelected = 1.3.3`
+    *   - `-Drelease=minor`, `-Dsnapshot=true`: `semVerSelected =
+    *     1.3.3-SNAPSHOT`
+    *   - `-Drelease=patch`: `semVerSelected = 1.2.4`
+    *   - `-Drelease=patch`, `-Dsnapshot=true`: `semVerSelected =
+    *     1.2.4-SNAPSHOT`
+    *   - `release` not set: `semVerSelected = 1.2.4-SNAPSHOT`
     */
-  lazy val workingVersion = settingKey[String](
-    "Revision level increment of the latest version, or 0.1.0 if no tags exist."
+  lazy val semVerSelected = settingKey[String](
+    "Version selected for the current build. Depends on the release type and current version."
+  )
+
+  /** SBT Setting for the selected major version. This value is always the major
+    * version part of the `semVerSelected` value.
+    */
+  lazy val semVerMajor = settingKey[Int](
+    "Major version selected for the current build. Depends on the release type and current version."
+  )
+
+  /** Task which emits the current and selected versions at the informational
+    * log level.
+    */
+  lazy val semVerInfo = taskKey[Unit](
+    "Dump the calculated version information."
   )
 
 }

src/main/scala/gs/SemVerPlugin.scala

@@ -1,6 +1,5 @@
 package gs
 
-import Keys._
 import sbt._
 
 object SemVerPlugin extends AutoPlugin {
@@ -10,9 +9,56 @@ object SemVerPlugin extends AutoPlugin {
 
   import autoImport._
 
-  /* override lazy val globalSettings: Seq[Setting[_]] = Seq( helloGreeting :=
-   * "hi", )
-   *
-   * override lazy val projectSettings: Seq[Setting[_]] = Seq( hello := { val s
-   * = streams.value val g = helloGreeting.value s.log.info(g) } ) */
+  // Perform all version calculations and expose as a variable.
+  lazy val semVerDefaults: Seq[Setting[_]] = {
+    // The latest semantic version relevant to this project, calculated by
+    // looking at the latest Git tag.
+    val latestSemVer =
+      Git.getLatestSemVer()
+
+    // The selected release type (if any), determined by looking at the SBT
+    // command line and checking if `-Drelease=<release-type>` was specified.
+    val releaseType =
+      PluginProperties.getReleaseType()
+
+    // See whether this is a pre-release build or not. If it is (if this value
+    // is true), the pre-release suffix `-SNAPSHOT` will be appended to the
+    // calculated version.
+    val isSnapshot =
+      PluginProperties.isSnapshot() || releaseType.isEmpty
+
+    // Calculate the appropriate semantic version for this build of the project.
+    val selectedSemVer = releaseType match {
+      case Some(ReleaseType.Major) => latestSemVer.incrementMajor()
+      case Some(ReleaseType.Minor) => latestSemVer.incrementMinor()
+      case Some(ReleaseType.Patch) => latestSemVer.incrementPatch()
+      case None                    =>
+        // Note: this doesn't play nicely with repositories that have
+        // pre-release versions before 0.1.0.
+        if (latestSemVer == SemVer.DefaultVersion)
+          latestSemVer
+        else
+          latestSemVer.incrementPatch()
+    }
+
+    // Expose the relevant values as setting keys.
+    Seq(
+      semVerCurrent  := latestSemVer.toString(),
+      semVerSelected := selectedSemVer.render(isSnapshot),
+      semVerMajor    := selectedSemVer.major
+    )
+  }
+
+  // Automatically exposed globally.
+  override lazy val globalSettings: Seq[Setting[_]] = semVerDefaults
+
+  // Add the custom task.
+  override lazy val buildSettings: Seq[Setting[_]] = Seq(
+    semVerInfo := {
+      val log = Keys.streams.value.log
+      log.info(s"[SemVer] Current: ${semVerCurrent.value}")
+      log.info(s"[SemVer] Selected: ${semVerSelected.value}")
+    }
+  )
+
 }