Move some more build logic to buildSrc

Look, I don't enjoy having 600 LOC long build.gradle files, it's just
very easy to do! This at least moves some of the complexity elsewhere,
so the build script is a little more declarative.

buildSrc/src/main/kotlin/cc/tweaked/gradle/CCTweakedExtension.kt

@@ -0,0 +1,124 @@
+package cc.tweaked.gradle
+
+import org.gradle.api.NamedDomainObjectProvider
+import org.gradle.api.Project
+import org.gradle.api.attributes.TestSuiteType
+import org.gradle.api.file.FileSystemOperations
+import org.gradle.api.provider.Provider
+import org.gradle.api.reporting.ReportingExtension
+import org.gradle.api.tasks.JavaExec
+import org.gradle.api.tasks.SourceSetContainer
+import org.gradle.configurationcache.extensions.capitalized
+import org.gradle.kotlin.dsl.get
+import org.gradle.language.base.plugins.LifecycleBasePlugin
+import org.gradle.testing.jacoco.plugins.JacocoCoverageReport
+import org.gradle.testing.jacoco.plugins.JacocoPluginExtension
+import org.gradle.testing.jacoco.plugins.JacocoTaskExtension
+import org.gradle.testing.jacoco.tasks.JacocoReport
+import java.io.BufferedWriter
+import java.io.IOException
+import java.io.OutputStreamWriter
+import java.util.regex.Pattern
+
+abstract class CCTweakedExtension(
+    private val project: Project,
+    private val fs: FileSystemOperations,
+) {
+    /** Get the hash of the latest git commit. */
+    val gitHash: Provider<String> = gitProvider(project) {
+        ProcessHelpers.captureOut("git", "-C", project.projectDir.absolutePath, "rev-parse", "HEAD")
+    }
+
+    /** Get the current git branch. */
+    val gitBranch: Provider<String> = gitProvider(project) {
+        ProcessHelpers.captureOut("git", "-C", project.projectDir.absolutePath, "rev-parse", "--abbrev-ref", "HEAD")
+    }
+
+    /** Get a list of all contributors to the project. */
+    val gitContributors: Provider<List<String>> = gitProvider(project) {
+        val authors: Set<String> = HashSet(
+            ProcessHelpers.captureLines(
+                "git", "-C", project.projectDir.absolutePath, "log",
+                "--format=tformat:%an <%ae>%n%cn <%ce>%n%(trailers:key=Co-authored-by,valueonly)",
+            ),
+        )
+        val process = ProcessHelpers.startProcess("git", "check-mailmap", "--stdin")
+        BufferedWriter(OutputStreamWriter(process.outputStream)).use { writer ->
+            for (authorName in authors) {
+                var author = authorName
+
+                if (author.isEmpty()) continue
+                if (!author.endsWith(">")) author += ">" // Some commits have broken Co-Authored-By lines!
+                writer.write(author)
+                writer.newLine()
+            }
+        }
+        val contributors: MutableSet<String> = HashSet()
+        for (authorLine in ProcessHelpers.captureLines(process)) {
+            val matcher = EMAIL.matcher(authorLine)
+            matcher.find()
+            val name = matcher.group(1)
+            if (!IGNORED_USERS.contains(name)) contributors.add(name)
+        }
+
+        contributors.sortedWith(String.CASE_INSENSITIVE_ORDER)
+    }
+
+    fun jacoco(task: NamedDomainObjectProvider<JavaExec>) {
+        val classDump = project.buildDir.resolve("jacocoClassDump/${task.name}")
+        val reportTaskName = "jacoco${task.name.capitalized()}Report"
+
+        val jacoco = project.extensions.getByType(JacocoPluginExtension::class.java)
+        task.configure {
+            finalizedBy(reportTaskName)
+
+            doFirst("Clean class dump directory") { fs.delete { delete(classDump) } }
+
+            jacoco.applyTo(this)
+            extensions.configure(JacocoTaskExtension::class.java) {
+                includes = listOf("dan200.computercraft.*")
+                classDumpDir = classDump
+
+                // Older versions of modlauncher don't include a protection domain (and thus no code
+                // source). Jacoco skips such classes by default, so we need to explicitly include them.
+                isIncludeNoLocationClasses = true
+            }
+        }
+
+        project.tasks.register(reportTaskName, JacocoReport::class.java) {
+            group = LifecycleBasePlugin.VERIFICATION_GROUP
+            description = "Generates code coverage report for the ${task.name} task."
+
+            executionData(task.get())
+            classDirectories.from(classDump)
+
+            // Don't want to use sourceSets(...) here as we have a custom class directory.
+            val sourceSets = project.extensions.getByType(SourceSetContainer::class.java)
+            sourceDirectories.from(sourceSets["main"].allSource.sourceDirectories)
+        }
+
+        project.extensions.configure(ReportingExtension::class.java) {
+            reports.register("${task.name}CodeCoverageReport", JacocoCoverageReport::class.java) {
+                testType.set(TestSuiteType.INTEGRATION_TEST)
+            }
+        }
+    }
+
+    companion object {
+        private val EMAIL = Pattern.compile("^([^<]+) <.+>$")
+        private val IGNORED_USERS = setOf(
+            "GitHub", "Daniel Ratcliffe", "Weblate",
+        )
+
+        private fun <T> gitProvider(project: Project, supplier: () -> T): Provider<T> {
+            return project.provider {
+                try {
+                    supplier()
+                } catch (e: IOException) {
+                    project.logger.error("Cannot read Git Repository", e)
+                    null
+                }
+            }
+        }
+    }
+}

buildSrc/src/main/kotlin/cc/tweaked/gradle/CCTweakedPlugin.kt

@@ -0,0 +1,13 @@
+package cc.tweaked.gradle
+
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+
+/**
+ * Configures projects to match a shared configuration.
+ */
+class CCTweakedPlugin : Plugin<Project> {
+    override fun apply(project: Project) {
+        project.extensions.create("cct", CCTweakedExtension::class.java)
+    }
+}

buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckChangelog.kt

@@ -0,0 +1,65 @@
+package cc.tweaked.gradle
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.GradleException
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.provider.Property
+import org.gradle.api.tasks.*
+import org.gradle.language.base.plugins.LifecycleBasePlugin
+import java.nio.charset.StandardCharsets
+
+/**
+ * Checks the `changelog.md` and `whatsnew.md` files are well-formed.
+ */
+@CacheableTask
+abstract class CheckChangelog : DefaultTask() {
+    init {
+        group = LifecycleBasePlugin.VERIFICATION_GROUP
+        description = "Verifies the changelog and whatsnew file are consistent."
+    }
+
+    @get:Input
+    abstract val version: Property<String>
+
+    @get:InputFile
+    @get:PathSensitive(PathSensitivity.NONE)
+    abstract val changelog: RegularFileProperty
+
+    @get:InputFile
+    @get:PathSensitive(PathSensitivity.NONE)
+    abstract val whatsNew: RegularFileProperty
+
+    @TaskAction
+    fun check() {
+        val version = version.get()
+
+        var ok = true
+
+        // Check we're targetting the current version
+        var whatsNew = whatsNew.get().asFile.readLines()
+        if (whatsNew[0] != "New features in CC: Tweaked $version") {
+            ok = false
+            logger.error("Expected `whatsnew.md' to target $version.")
+        }
+
+        // Check "read more" exists and trim it
+        val idx = whatsNew.indexOfFirst { it == "Type \"help changelog\" to see the full version history." }
+        if (idx == -1) {
+            ok = false
+            logger.error("Must mention the changelog in whatsnew.md")
+        } else {
+            whatsNew = whatsNew.slice(0 until idx)
+        }
+
+        // Check whatsnew and changelog match.
+        val expectedChangelog = sequenceOf("# ${whatsNew[0]}") + whatsNew.slice(1 until whatsNew.size).asSequence()
+        val changelog = changelog.get().asFile.readLines()
+        val mismatch = expectedChangelog.zip(changelog.asSequence()).filter { (a, b) -> a != b }.firstOrNull()
+        if (mismatch != null) {
+            ok = false
+            logger.error("whatsnew and changelog are not in sync")
+        }
+
+        if (!ok) throw GradleException("Could not check release")
+    }
+}

buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckLicense.kt

@@ -25,7 +25,7 @@ object LicenseHeader {
     )
 
     private fun getTemplateText(file: File): String =
-        file.readText(StandardCharsets.UTF_8).trim().replace("\${year}", "$YEAR")
+        file.readText().trim().replace("\${year}", "$YEAR")
 
     private fun formatFile(licenses: Licenses, contents: String, file: File): String {
         val license = getLicense(contents)
@@ -38,8 +38,8 @@ object LicenseHeader {
         }
     }
 
-    private fun getExpectedLicense(licenses: Licenses, file: File): String {
-        var file: File? = file
+    private fun getExpectedLicense(licenses: Licenses, root: File): String {
+        var file: File? = root
         while (file != null) {
             if (file.name == "api" && file.parentFile?.name == "computercraft") return licenses.api
             file = file.parentFile

buildSrc/src/main/kotlin/cc/tweaked/gradle/ProcessHelpers.kt

@@ -0,0 +1,34 @@
+package cc.tweaked.gradle
+
+import org.codehaus.groovy.runtime.ProcessGroovyMethods
+import java.io.BufferedReader
+import java.io.IOException
+import java.io.InputStreamReader
+
+internal object ProcessHelpers {
+    fun startProcess(vararg command: String): Process {
+        // Something randomly passes in "GIT_DIR=" as an environment variable which clobbers everything else. Don't
+        // inherit the environment array!
+        return Runtime.getRuntime().exec(command, arrayOfNulls(0))
+    }
+
+    fun captureOut(vararg command: String): String {
+        val process = startProcess(*command)
+        val result = ProcessGroovyMethods.getText(process)
+        if (process.waitFor() != 0) throw IOException("Command exited with a non-0 status")
+        return result
+    }
+
+    fun captureLines(vararg command: String): List<String> {
+        return captureLines(startProcess(*command))
+    }
+
+    fun captureLines(process: Process): List<String> {
+        val out = BufferedReader(InputStreamReader(process.inputStream)).use { reader ->
+            reader.lines().filter { it.isNotEmpty() }.toList()
+        }
+        ProcessGroovyMethods.closeStreams(process)
+        if (process.waitFor() != 0) throw IOException("Command exited with a non-0 status")
+        return out
+    }
+}