Add optional auto merge job

src/main/scala/sbtghactions/GenerativeKeys.scala

@@ -42,7 +42,7 @@ trait GenerativeKeys {
 
   lazy val githubWorkflowPublishPreamble = settingKey[Seq[WorkflowStep]]("A list of steps to insert after base setup but before publishing (default: [])")
   lazy val githubWorkflowPublishPostamble = settingKey[Seq[WorkflowStep]]("A list of steps to insert after publication but before the end of the publish job (default: [])")
-  lazy val githubWorkflowPublish = settingKey[Seq[WorkflowStep]]("A sequence workflow steps which publishe the project (default: [Sbt(List(\"+publish\"))])")
+  lazy val githubWorkflowPublish = settingKey[Seq[WorkflowStep]]("A sequence workflow steps which publish the project (default: [Sbt(List(\"+publish\"))])")
   lazy val githubWorkflowPublishTargetBranches = settingKey[Seq[RefPredicate]]("A set of branch predicates which will be applied to determine whether the current branch gets a publication stage; if empty, publish will be skipped entirely (default: [== master])")
   lazy val githubWorkflowPublishCond = settingKey[Option[String]]("A set of conditionals to apply to the publish job to further restrict its run (default: [])")
 
@@ -58,8 +58,12 @@ trait GenerativeKeys {
   lazy val githubWorkflowArtifactUpload = settingKey[Boolean]("Controls whether or not to upload target directories in the event that multiple jobs are running sequentially. Can be set on a per-project basis (default: true)")
   lazy val githubWorkflowJobSetup = settingKey[Seq[WorkflowStep]]("The automatically-generated checkout, setup, and cache steps which are common to all jobs which touch the build (default: autogenerated)")
 
-  lazy val githubWorkflowEnv = settingKey[Map[String, String]](s"A map of static environment variable assignemnts global to the workflow (default: { GITHUB_TOKEN: $${{ secrets.GITHUB_TOKEN }} })")
+  lazy val githubWorkflowEnv = settingKey[Map[String, String]]("A map of static environment variable assignments global to the workflow (default: { GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} })")
   lazy val githubWorkflowAddedJobs = settingKey[Seq[WorkflowJob]]("A list of additional jobs to add to the CI workflow (default: [])")
+
+  lazy val githubWorkflowAutoMerge = settingKey[Boolean]("Whether or not to enable auto merging of bot PRs, e.g. by scala-steward (default: false)")
+  lazy val githubWorkflowAutoMergeAuthor = settingKey[String]("The user name of a bot whose PRs will be merged automatically (default: scala-steward)")
+  lazy val githubWorkflowAutoMergeMethod = settingKey[MergeMethod]("The merge method to use for auto merging bot PRs (default: Squash)")
 }
 
 object GenerativeKeys extends GenerativeKeys

src/main/scala/sbtghactions/GenerativePlugin.scala

@@ -383,7 +383,12 @@ ${indent(jobs.map(compileJob(_, sbt)).mkString("\n\n"), 1)}"""
     githubWorkflowTargetTags := Seq(),
 
     githubWorkflowEnv := Map("GITHUB_TOKEN" -> s"$${{ secrets.GITHUB_TOKEN }}"),
-    githubWorkflowAddedJobs := Seq())
+    githubWorkflowAddedJobs := Seq(),
+
+    githubWorkflowAutoMerge := false,
+    githubWorkflowAutoMergeAuthor := "scala-steward",
+    githubWorkflowAutoMergeMethod := MergeMethod.Squash
+  )
 
   private lazy val internalTargetAggregation = settingKey[Seq[File]]("Aggregates target directories from all subprojects")
 
@@ -543,6 +548,25 @@ ${indent(jobs.map(compileJob(_, sbt)).mkString("\n\n"), 1)}"""
           javas = List(githubWorkflowJavaVersions.value.head),
           needs = List("build"))).filter(_ => !githubWorkflowPublishTargetBranches.value.isEmpty)
 
+      val autoMergeOpt = if (githubWorkflowAutoMerge.value)
+        WorkflowJob(
+          id = "merge",
+          name = "Merge automatically",
+          steps = WorkflowStep.Use(
+            owner = "ridedott",
+            repo = "merge-me-action",
+            ref = "v1",
+            params = Map(
+              "GITHUB_LOGIN" -> githubWorkflowAutoMergeAuthor.value,
+              "GITHUB_TOKEN" -> "${{ secrets.GITHUB_TOKEN }}",
+              "MERGE_METHOD" -> githubWorkflowAutoMergeMethod.value.value
+            )
+          ) :: Nil,
+          needs = List("build")
+        ) :: Nil
+      else
+        Nil
+
       Seq(
         WorkflowJob(
           "build",
@@ -562,7 +586,8 @@ ${indent(jobs.map(compileJob(_, sbt)).mkString("\n\n"), 1)}"""
           matrixAdds = githubWorkflowBuildMatrixAdditions.value,
           matrixIncs = githubWorkflowBuildMatrixInclusions.value.toList,
           matrixExcs = githubWorkflowBuildMatrixExclusions.value.toList,
-          runsOnExtraLabels = githubWorkflowBuildRunsOnExtraLabels.value.toList )) ++ publishJobOpt ++ githubWorkflowAddedJobs.value
+          runsOnExtraLabels = githubWorkflowBuildRunsOnExtraLabels.value.toList )
+      ) ++ autoMergeOpt ++ publishJobOpt ++ githubWorkflowAddedJobs.value
     })
 
   private val generateCiContents = Def task {

src/main/scala/sbtghactions/MergeMethod.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2020 Daniel Spiewak
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sbtghactions
+
+sealed trait MergeMethod {
+  final def value: String = toString.toUpperCase
+}
+
+object MergeMethod {
+  case object Merge extends MergeMethod
+  case object Squash extends MergeMethod
+  case object Rebase extends MergeMethod
+}

src/sbt-test/sbtghactions/check-and-regenerate/build.sbt

@@ -20,3 +20,4 @@ ThisBuild / githubWorkflowBuildMatrixExclusions +=
 
 ThisBuild / githubWorkflowBuild += WorkflowStep.Run(List("echo yo"))
 ThisBuild / githubWorkflowPublish += WorkflowStep.Run(List("echo sup"))
+ThisBuild / githubWorkflowAutoMerge := true

src/sbt-test/sbtghactions/check-and-regenerate/expected-ci.yml

@@ -73,6 +73,22 @@ jobs:
           name: target-${{ matrix.os }}-${{ matrix.scala }}-${{ matrix.java }}
           path: targets.tar
 
+  merge:
+    name: Merge automatically
+    needs: [build]
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        scala: [2.13.1]
+        java: [[email protected]]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: ridedott/merge-me-action@v1
+        with:
+          GITHUB_LOGIN: scala-steward
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          MERGE_METHOD: SQUASH
+
   publish:
     name: Publish Artifacts
     needs: [build]