Refactor pull request head: replace conditionals with polymorphism

This is another example of replacing conditionals with polymorphism on
`ForgeType`. This was a theme in commit b42866b, merged in this PR back
in August 2023:

scala-steward-org#3145

A benefit of this pattern is as new types of forge are implemented, the
responsibilities for supporting that new `ForgeType` are all in one
place, rather than spread across several methods elsewhere in the
codebase.

To confess, I think there's probably a further refactor that could be
done, to introduce a better parameter object denoting a 'Pull Request
Head' (that conceivably could better model the way that some
`ForgeType`s don't even support forking) - but that can wait for
another day, fixing scala-steward-org#3300 is more urgent!

modules/core/src/main/scala/org/scalasteward/core/forge/ForgeType.scala

@@ -21,9 +21,13 @@ import cats.syntax.all._
 import org.http4s.Uri
 import org.http4s.syntax.literals._
 import org.scalasteward.core.application.Config.ForgeCfg
+import org.scalasteward.core.data.Repo
 import org.scalasteward.core.forge.ForgeType._
+import org.scalasteward.core.git.Branch
 import org.scalasteward.core.util.unexpectedString
 
+import scala.annotation.nowarn
+
 sealed trait ForgeType extends Product with Serializable {
   def publicWebHost: Option[String]
 
@@ -41,6 +45,11 @@ sealed trait ForgeType extends Product with Serializable {
   def supportsForking: Boolean = true
   def supportsLabels: Boolean = true
 
+  /** Determines the `head` (GitHub) / `source_branch` (GitLab, Bitbucket) parameter for searching
+    * for already existing pull requests or creating new pull requests.
+    */
+  def pullRequestHeadFor(@nowarn fork: Repo, updateBranch: Branch): String = updateBranch.name
+
   val asString: String = this match {
     case AzureRepos      => "azure-repos"
     case Bitbucket       => "bitbucket"
@@ -94,6 +103,8 @@ object ForgeType {
     val publicApiBaseUrl = uri"https://api.github.com"
     val diffs: DiffUriPattern = (from, to) => _ / "compare" / s"$from...$to"
     val files: FileUriPattern = fileName => _ / "blob" / "master" / fileName
+    override def pullRequestHeadFor(fork: Repo, updateBranch: Branch): String =
+      s"${fork.owner}:${updateBranch.name}"
   }
 
   case object GitLab extends ForgeType {

modules/core/src/main/scala/org/scalasteward/core/nurture/NurtureAlg.scala

@@ -31,7 +31,7 @@ import org.scalasteward.core.git.{Branch, Commit, GitAlg}
 import org.scalasteward.core.repoconfig.PullRequestUpdateStrategy
 import org.scalasteward.core.util.logger.LoggerOps
 import org.scalasteward.core.util.{Nel, UrlChecker}
-import org.scalasteward.core.{forge, git, util}
+import org.scalasteward.core.{git, util}
 import org.typelevel.log4cats.Logger
 
 final class NurtureAlg[F[_]](config: ForgeCfg)(implicit
@@ -92,7 +92,7 @@ final class NurtureAlg[F[_]](config: ForgeCfg)(implicit
   private def processUpdate(data: UpdateData): F[ProcessResult] =
     for {
       _ <- logger.info(s"Process update ${data.update.show}")
-      head = forge.headFor(config.tpe, data.fork, data.updateBranch)
+      head = config.tpe.pullRequestHeadFor(data.fork, data.updateBranch)
       pullRequests <- forgeApiAlg.listPullRequests(data.repo, head, data.baseBranch)
       result <- pullRequests.headOption match {
         case Some(pr) if pr.state.isClosed && data.update.isInstanceOf[Update.Single] =>
@@ -230,20 +230,18 @@ final class NurtureAlg[F[_]](config: ForgeCfg)(implicit
           .on(u => List(u.currentVersion.value), _.updates.map(_.currentVersion.value))
           .flatTraverse(gitAlg.findFilesContaining(data.repo, _))
           .map(_.distinct)
-      branchName = forge.headFor(config.tpe, data.fork, data.updateBranch)
       allLabels = labelsFor(data.update, edits, filesWithOldVersion, artifactIdToVersionScheme)
       labels = filterLabels(allLabels, data.repoData.config.pullRequests.includeMatchedLabels)
-      requestData = NewPullRequestData.from(
-        data = data,
-        branchName = branchName,
-        edits = edits,
-        artifactIdToUrl = artifactIdToUrl,
-        artifactIdToUpdateInfoUrls = artifactIdToUpdateInfoUrls.toMap,
-        filesWithOldVersion = filesWithOldVersion,
-        addLabels = config.addLabels,
-        labels = data.repoData.config.pullRequests.customLabels ++ labels
-      )
-    } yield requestData
+    } yield NewPullRequestData.from(
+      data = data,
+      branchName = config.tpe.pullRequestHeadFor(data.fork, data.updateBranch),
+      edits = edits,
+      artifactIdToUrl = artifactIdToUrl,
+      artifactIdToUpdateInfoUrls = artifactIdToUpdateInfoUrls.toMap,
+      filesWithOldVersion = filesWithOldVersion,
+      addLabels = config.addLabels,
+      labels = data.repoData.config.pullRequests.customLabels ++ labels
+    )
 
   private def createPullRequest(data: UpdateData, edits: List[EditAttempt]): F[ProcessResult] =
     for {

modules/core/src/test/scala/org/scalasteward/core/forge/ForgePackageTest.scala → modules/core/src/test/scala/org/scalasteward/core/forge/ForgeTypeTest.scala

@@ -6,27 +6,24 @@ import org.scalasteward.core.data.{Repo, Update}
 import org.scalasteward.core.forge.ForgeType.{GitHub, GitLab}
 import org.scalasteward.core.git
 
-class ForgePackageTest extends FunSuite {
+class ForgeTypeTest extends FunSuite {
   private val repo = Repo("foo", "bar")
 
   // Single updates
 
   {
-
     val update = ("ch.qos.logback".g % "logback-classic".a % "1.2.0" %> "1.2.3").single
     val updateBranch = git.branchFor(update, None)
 
     test("headFor (single)") {
-      assertEquals(headFor(GitHub, repo, updateBranch), s"foo:${updateBranch.name}")
-      assertEquals(headFor(GitLab, repo, updateBranch), updateBranch.name)
+      assertEquals(GitHub.pullRequestHeadFor(repo, updateBranch), s"foo:${updateBranch.name}")
+      assertEquals(GitLab.pullRequestHeadFor(repo, updateBranch), updateBranch.name)
     }
-
   }
 
   // Grouped updates
 
   {
-
     val update = Update.Grouped(
       name = "my-group",
       title = None,
@@ -36,8 +33,8 @@ class ForgePackageTest extends FunSuite {
     val updateBranch = git.branchFor(update, None)
 
     test("headFor (grouped)") {
-      assertEquals(headFor(GitHub, repo, updateBranch), s"foo:update/my-group")
-      assertEquals(headFor(GitLab, repo, updateBranch), updateBranch.name)
+      assertEquals(GitHub.pullRequestHeadFor(repo, updateBranch), s"foo:update/my-group")
+      assertEquals(GitLab.pullRequestHeadFor(repo, updateBranch), updateBranch.name)
     }
   }
 
@@ -53,8 +50,8 @@ class ForgePackageTest extends FunSuite {
     val updateBranch = git.branchFor(update, None)
 
     test("headFor (grouped) with $hash") {
-      assertEquals(headFor(GitHub, repo, updateBranch), s"foo:update/my-group-1164623676")
-      assertEquals(headFor(GitLab, repo, updateBranch), updateBranch.name)
+      assertEquals(GitHub.pullRequestHeadFor(repo, updateBranch), s"foo:update/my-group-1164623676")
+      assertEquals(GitLab.pullRequestHeadFor(repo, updateBranch), updateBranch.name)
     }
   }