Reset instead of merge to update branches

Closes #3218

Author: fthomas

modules/core/src/main/scala/org/scalasteward/core/git/FileGitAlg.scala

@@ -97,7 +97,7 @@ final class FileGitAlg[F[_]](config: GitCfg)(implicit
 
   override def hasConflicts(repo: File, branch: Branch, base: Branch): F[Boolean] = {
     val tryMerge = git_("merge", "--no-commit", "--no-ff", branch.name)(repo)
-    val abortMerge = git_("merge", "--abort")(repo).void
+    val abortMerge = git_("merge", "--abort")(repo).attempt.void
 
     returnToCurrentBranch(repo) {
       checkoutBranch(repo, base) >> F.guarantee(tryMerge, abortMerge).attempt.map(_.isLeft)
@@ -114,41 +114,14 @@ final class FileGitAlg[F[_]](config: GitCfg)(implicit
     git("rev-parse", "--verify", branch.name)(repo)
       .flatMap(lines => F.fromEither(Sha1.from(lines.mkString("").trim)))
 
-  override def mergeTheirs(repo: File, branch: Branch): F[Option[Commit]] =
-    for {
-      before <- latestSha1(repo, Branch.head)
-      _ <- git_("merge", "--strategy-option=theirs", sign, branch.name)(repo).void
-        .handleErrorWith { throwable =>
-          // Resolve CONFLICT (modify/delete) by deleting unmerged files:
-          for {
-            unmergedFiles <- git("diff", "--name-only", "--diff-filter=U")(repo)
-            _ <- Nel
-              .fromList(unmergedFiles.filter(_.nonEmpty))
-              .fold(F.raiseError[Unit](throwable))(_.traverse_(file => git_("rm", file)(repo)))
-            _ <- git_("commit", "--all", "--no-edit", sign)(repo)
-          } yield ()
-        }
-      after <- latestSha1(repo, Branch.head)
-    } yield Option.when(before =!= after)(Commit(after))
-
   override def push(repo: File, branch: Branch): F[Unit] =
     git_("push", "--force", "--set-upstream", "origin", branch.name)(repo).void
 
   override def removeClone(repo: File): F[Unit] =
     fileAlg.deleteForce(repo)
 
-  override def revertChanges(repo: File, base: Branch): F[Option[Commit]] = {
-    val range = dotdot(base, Branch.head)
-    git("log", "--pretty=format:%h %p", range)(repo).flatMap { commitsWithParents =>
-      val commitsUntilMerge = commitsWithParents.map(_.split(' ')).takeWhile(_.length === 2)
-      val commits = commitsUntilMerge.flatMap(_.headOption)
-      if (commits.isEmpty) F.pure(None)
-      else {
-        val msg = CommitMsg(s"Revert commit(s) " + commits.mkString(", "))
-        git_("revert" :: "--no-commit" :: commits: _*)(repo) >> commitAllIfDirty(repo, msg)
-      }
-    }
-  }
+  override def resetHard(repo: File, base: Branch): F[Unit] =
+    git_("reset", "--hard", base.name)(repo).void
 
   override def setAuthor(repo: File, author: Author): F[Unit] =
     for {

modules/core/src/main/scala/org/scalasteward/core/git/GenGitAlg.scala

@@ -66,14 +66,11 @@ trait GenGitAlg[F[_], Repo] {
 
   def latestSha1(repo: Repo, branch: Branch): F[Sha1]
 
-  /** Merges `branch` into the current branch using `theirs` as merge strategy option. */
-  def mergeTheirs(repo: Repo, branch: Branch): F[Option[Commit]]
-
   def push(repo: Repo, branch: Branch): F[Unit]
 
   def removeClone(repo: Repo): F[Unit]
 
-  def revertChanges(repo: Repo, base: Branch): F[Option[Commit]]
+  def resetHard(repo: Repo, base: Branch): F[Unit]
 
   def setAuthor(repo: Repo, author: Author): F[Unit]
 
@@ -152,17 +149,14 @@ trait GenGitAlg[F[_], Repo] {
       override def latestSha1(repo: A, branch: Branch): F[Sha1] =
         f(repo).flatMap(self.latestSha1(_, branch))
 
-      override def mergeTheirs(repo: A, branch: Branch): F[Option[Commit]] =
-        f(repo).flatMap(self.mergeTheirs(_, branch))
-
       override def push(repo: A, branch: Branch): F[Unit] =
         f(repo).flatMap(self.push(_, branch))
 
       override def removeClone(repo: A): F[Unit] =
         f(repo).flatMap(self.removeClone)
 
-      override def revertChanges(repo: A, base: Branch): F[Option[Commit]] =
-        f(repo).flatMap(self.revertChanges(_, base))
+      override def resetHard(repo: A, base: Branch): F[Unit] =
+        f(repo).flatMap(self.resetHard(_, base))
 
       override def setAuthor(repo: A, author: Author): F[Unit] =
         f(repo).flatMap(self.setAuthor(_, author))

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

@@ -267,7 +267,7 @@ final class NurtureAlg[F[_]](config: ForgeCfg)(implicit
       gitAlg.returnToCurrentBranch(data.repo) {
         gitAlg.checkoutBranch(data.repo, data.updateBranch) >>
           shouldBeUpdated(data).ifM(
-            ifTrue = mergeAndApplyAgain(number, data),
+            ifTrue = resetAndApplyAgain(number, data),
             ifFalse = (Ignored: ProcessResult).pure
           )
       }
@@ -293,22 +293,19 @@ final class NurtureAlg[F[_]](config: ForgeCfg)(implicit
     result.flatMap { case (update, msg) => logger.info(msg).as(update) }
   }
 
-  private def mergeAndApplyAgain(number: PullRequestNumber, data: UpdateData): F[ProcessResult] =
+  private def resetAndApplyAgain(number: PullRequestNumber, data: UpdateData): F[ProcessResult] =
     for {
       _ <- logger.info(
-        s"Merge branch ${data.baseBranch.name} into ${data.updateBranch.name} and apply again"
+        s"Reset ${data.updateBranch.name} to ${data.baseBranch.name} and apply again"
       )
-      maybeRevertCommit <- gitAlg.revertChanges(data.repo, data.baseBranch)
-      maybeMergeCommit <- gitAlg.mergeTheirs(data.repo, data.baseBranch)
+      _ <- gitAlg.resetHard(data.repo, data.baseBranch)
       edits <- data.update.on(
         update = editAlg.applyUpdate(data.repoData, _),
         grouped = _.updates.flatTraverse(editAlg.applyUpdate(data.repoData, _))
       )
       editCommits = edits.flatMap(_.commits)
-      commits = maybeRevertCommit.toList ++ maybeMergeCommit.toList ++ editCommits
-      result <- pushCommits(data, commits)
+      result <- pushCommits(data, editCommits)
       requestData <- preparePullRequest(data, edits)
       _ <- forgeApiAlg.updatePullRequest(number: PullRequestNumber, data.repo, requestData)
     } yield result
-
 }

modules/core/src/test/scala/org/scalasteward/core/git/FileGitAlgTest.scala

@@ -6,7 +6,13 @@ import cats.effect.IO
 import cats.syntax.all._
 import munit.CatsEffectSuite
 import org.scalasteward.core.TestInstances.ioLogger
-import org.scalasteward.core.git.FileGitAlgTest.{ioAuxGitAlg, ioGitAlg, master}
+import org.scalasteward.core.git.FileGitAlgTest.{
+  conflictsNo,
+  conflictsYes,
+  ioAuxGitAlg,
+  ioGitAlg,
+  master
+}
 import org.scalasteward.core.io.FileAlgTest.ioFileAlg
 import org.scalasteward.core.io.ProcessAlgTest.ioProcessAlg
 import org.scalasteward.core.io.{FileAlg, ProcessAlg, WorkspaceAlg}
@@ -47,7 +53,7 @@ class FileGitAlgTest extends CatsEffectSuite {
     for {
       _ <- ioAuxGitAlg.createRepo(repo)
       _ <- ioAuxGitAlg.createConflict(repo)
-      authors <- ioGitAlg.branchAuthors(repo, Branch("conflicts-no"), master)
+      authors <- ioGitAlg.branchAuthors(repo, conflictsNo, master)
       _ = assertEquals(authors, List("'Bot Doe'"))
     } yield ()
   }
@@ -157,57 +163,37 @@ class FileGitAlgTest extends CatsEffectSuite {
     for {
       _ <- ioAuxGitAlg.createRepo(repo)
       _ <- ioAuxGitAlg.createConflict(repo)
-      c1 <- ioGitAlg.hasConflicts(repo, Branch("conflicts-yes"), master)
-      c2 <- ioGitAlg.hasConflicts(repo, Branch("conflicts-no"), master)
+      c1 <- ioGitAlg.hasConflicts(repo, conflictsYes, master)
+      c2 <- ioGitAlg.hasConflicts(repo, conflictsNo, master)
       _ = assertEquals((c1, c2), (true, false))
     } yield ()
   }
 
-  test("mergeTheirs") {
-    val repo = rootDir / "mergeTheirs"
+  test("isMerged") {
+    val repo = rootDir / "isMerged"
     for {
       _ <- ioAuxGitAlg.createRepo(repo)
       _ <- ioAuxGitAlg.createConflict(repo)
-      branch = Branch("conflicts-yes")
-      c1 <- ioGitAlg.hasConflicts(repo, branch, master)
-      m1 <- ioGitAlg.isMerged(repo, master, branch)
-      _ <- ioGitAlg.checkoutBranch(repo, branch)
-      _ <- ioGitAlg.mergeTheirs(repo, master)
-      c2 <- ioGitAlg.hasConflicts(repo, branch, master)
-      m2 <- ioGitAlg.isMerged(repo, master, branch)
-      _ = assertEquals((c1, m1, c2, m2), (true, false, false, true))
-    } yield ()
-  }
-
-  test("mergeTheirs: CONFLICT (modify/delete)") {
-    val repo = rootDir / "mergeTheirs-modify-delete"
-    for {
-      _ <- ioAuxGitAlg.createRepo(repo)
-      _ <- ioAuxGitAlg.createConflictFileRemovedOnMaster(repo)
-      branch = Branch("conflicts-yes")
-      c1 <- ioGitAlg.hasConflicts(repo, branch, master)
-      m1 <- ioGitAlg.isMerged(repo, master, branch)
-      _ <- ioGitAlg.checkoutBranch(repo, branch)
-      _ <- ioGitAlg.mergeTheirs(repo, master)
-      c2 <- ioGitAlg.hasConflicts(repo, branch, master)
-      m2 <- ioGitAlg.isMerged(repo, master, branch)
-      _ = assertEquals((c1, m1, c2, m2), (true, false, false, true))
+      m1 <- ioGitAlg.isMerged(repo, conflictsNo, master)
+      _ <- ioAuxGitAlg.git("merge", conflictsNo.name)(repo)
+      m2 <- ioGitAlg.isMerged(repo, conflictsNo, master)
+      _ = assertEquals((m1, m2), (false, true))
     } yield ()
   }
 
-  test("revertChanges") {
-    val repo = rootDir / "revertChanges"
+  test("resetHard") {
+    val repo = rootDir / "resetHard"
     for {
       _ <- ioAuxGitAlg.createRepo(repo)
       _ <- ioAuxGitAlg.createConflict(repo)
-      branch = Branch("conflicts-yes")
+      branch = conflictsYes
       c1 <- ioGitAlg.hasConflicts(repo, branch, master)
       d1 <- ioGitAlg.branchesDiffer(repo, master, branch)
       _ <- ioGitAlg.checkoutBranch(repo, branch)
-      _ <- ioGitAlg.revertChanges(repo, master)
+      _ <- ioGitAlg.resetHard(repo, master)
       c2 <- ioGitAlg.hasConflicts(repo, branch, master)
       d2 <- ioGitAlg.branchesDiffer(repo, master, branch)
-      _ = assertEquals((c1, d1, c2, d2), (true, true, false, true))
+      _ = assertEquals((c1, d1, c2, d2), (true, true, false, false))
     } yield ()
   }
 
@@ -217,7 +203,9 @@ class FileGitAlgTest extends CatsEffectSuite {
 }
 
 object FileGitAlgTest {
-  val master: Branch = Branch("master")
+  private val master: Branch = Branch("master")
+  private val conflictsNo: Branch = Branch("conflicts-no")
+  private val conflictsYes: Branch = Branch("conflicts-yes")
 
   final class AuxGitAlg[F[_]](implicit
       fileAlg: FileAlg[F],
@@ -250,13 +238,13 @@ object FileGitAlgTest {
         _ <- fileAlg.writeFile(repo / "file2", "file2, line1")
         _ <- addFiles(repo, repo / "file1", repo / "file2")
         // work on conflicts-no
-        _ <- gitAlg.createBranch(repo, Branch("conflicts-no"))
+        _ <- gitAlg.createBranch(repo, conflictsNo)
         _ <- fileAlg.writeFile(repo / "file3", "file3, line1")
         _ <- git("add", "file3")(repo)
         _ <- gitAlg.commitAll(repo, CommitMsg("Add file3 on conflicts-no"))
         _ <- gitAlg.checkoutBranch(repo, master)
         // work on conflicts-yes
-        _ <- gitAlg.createBranch(repo, Branch("conflicts-yes"))
+        _ <- gitAlg.createBranch(repo, conflictsYes)
         _ <- fileAlg.writeFile(repo / "file2", "file2, line1\nfile2, line2 on conflicts-yes")
         _ <- git("add", "file2")(repo)
         _ <- gitAlg.commitAll(repo, CommitMsg("Modify file2 on conflicts-yes"))
@@ -274,7 +262,7 @@ object FileGitAlgTest {
         _ <- fileAlg.writeFile(repo / "file2", "file2, line1")
         _ <- addFiles(repo, repo / "file1", repo / "file2")
         // work on conflicts-yes
-        _ <- gitAlg.createBranch(repo, Branch("conflicts-yes"))
+        _ <- gitAlg.createBranch(repo, conflictsYes)
         _ <- fileAlg.writeFile(repo / "file2", "file2, line1\nfile2, line2 on conflicts-yes")
         _ <- git("add", "file2")(repo)
         _ <- gitAlg.commitAll(repo, CommitMsg("Modify file2 on conflicts-yes"))