diff -r 000000000000 -r 0a13dcabf7d3 buildSrc/src/main/kotlin/RepositoryChangeset.kt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/buildSrc/src/main/kotlin/RepositoryChangeset.kt	Fri Apr 14 14:29:05 2023 -0400
@@ -0,0 +1,156 @@
+/*
+ * AboutOss is a utility library to retrieve and display
+ * opensource licenses in Android applications.
+ *
+ * Copyright (C) 2023 by Frederic-Charles Barthelery.
+ *
+ * This file is part of AboutOss.
+ *
+ * AboutOss is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * AboutOss is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with AboutOss.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.geekorum.build
+
+import com.android.build.api.variant.ApplicationAndroidComponentsExtension
+import com.android.build.api.variant.BuildConfigField
+import com.android.build.api.variant.VariantOutputConfiguration.OutputType
+import org.gradle.api.DefaultTask
+import org.gradle.api.Project
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.provider.Property
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+import org.gradle.configurationcache.extensions.capitalized
+import org.gradle.kotlin.dsl.register
+import org.gradle.process.ExecOperations
+import java.io.ByteArrayOutputStream
+import java.io.File
+import javax.inject.Inject
+
+internal fun ExecOperations.getGitSha1(projectDir: File): String? = runCommand("git rev-parse HEAD", workingDir = projectDir)?.trim()
+
+internal fun ExecOperations.getHgSha1(projectDir: File): String? = runCommand("hg id --debug -i -r .", workingDir = projectDir)?.trim()
+
+internal fun ExecOperations.getHgLocalRevisionNumber(projectDir: File): String? = runCommand("hg id -n -r .", workingDir = projectDir)?.trim()
+
+private fun ExecOperations.getChangeSet(projectDir: File): String {
+    val git = File(projectDir, ".git")
+    val hg = File(projectDir, ".hg")
+    return when {
+        git.exists() -> "git:${getGitSha1(projectDir)}"
+        hg.exists() -> "hg:${getHgSha1(projectDir)}"
+        else -> "unknown"
+    }
+}
+
+/**
+ * Compute a version code following this format : MmmPBBB
+ * M is major, mm is minor, P is patch
+ * BBB is build version number from hg
+ */
+private fun ExecOperations.computeChangesetVersionCode(projectDir: File, major: Int = 0, minor: Int = 0, patch: Int = 0): Int {
+    val base = (major * 1000000) + (minor * 10000) + (patch * 1000)
+    return base + (getHgLocalRevisionNumber(projectDir)?.trim()?.toIntOrNull() ?: 0)
+}
+
+private fun ExecOperations.runCommand(
+    command: String,
+    workingDir: File = File(".")
+): String? {
+    val output = ByteArrayOutputStream()
+    val result = exec {
+        commandLine(command.split("\\s".toRegex()))
+        setWorkingDir(workingDir)
+        setStandardOutput(output)
+        setErrorOutput(output)
+    }
+    result.rethrowFailure()
+    return output.toString(Charsets.UTF_8)
+}
+
+abstract class VersionCodeTask : DefaultTask() {
+
+    @get:OutputFile
+    abstract val versionCodeOutputFile: RegularFileProperty
+
+    @get:OutputFile
+    abstract val changesetOutputFile: RegularFileProperty
+
+    @get:Input
+    abstract val repositoryDirectory: Property<String>
+
+    @get:Input
+    abstract val major: Property<Int>
+
+    @get:Input
+    abstract val minor: Property<Int>
+
+    @get:Input
+    abstract val patch: Property<Int>
+
+    @get:Inject
+    abstract val exec: ExecOperations
+
+    @TaskAction
+    fun computeVersionCode() {
+        val projectDir = File(repositoryDirectory.get())
+        val versionCode = exec.computeChangesetVersionCode(projectDir, major.getOrElse(0), minor.getOrElse(0), patch.getOrElse(0))
+        versionCodeOutputFile.get().asFile.writeText("$versionCode")
+    }
+
+    @TaskAction
+    fun computeChangeset() {
+        val projectDir = File(repositoryDirectory.get())
+        val changeset = exec.getChangeSet(projectDir)
+        changesetOutputFile.get().asFile.writeText(changeset)
+    }
+}
+
+/**
+ * @param versionNameSuffix extra string to add to version name
+ */
+fun ApplicationAndroidComponentsExtension.configureVersionChangeset(project: Project, major: Int, minor: Int, patch: Int, versionNameSuffix: String = "") {
+    // Note: Everything in there is incubating.
+
+    // onVariantProperties registers an action that configures variant properties during
+    // variant computation (which happens during afterEvaluate)
+    onVariants {
+        // Because app module can have multiple output when using mutli-APK, versionCode/Name
+        // are only available on the variant output.
+        // Here gather the output when we are in single mode (ie no multi-apk)
+        val mainOutput = it.outputs.single { it.outputType == OutputType.SINGLE }
+
+        // create version Code generating task
+        val versionCodeTask = project.tasks.register<VersionCodeTask>("computeVersionCodeFor${it.name.capitalized()}") {
+            this.major.set(major)
+            this.minor.set(minor)
+            this.patch.set(patch)
+            repositoryDirectory.set(project.rootDir.absolutePath)
+            versionCodeOutputFile.set(project.layout.buildDirectory.file("intermediates/versionCode.txt"))
+            changesetOutputFile.set(project.layout.buildDirectory.file("intermediates/changeset.txt"))
+        }
+
+        // wire version code from the task output
+        // map will create a lazy Provider that
+        // 1. runs just before the consumer(s), ensuring that the producer (VersionCodeTask) has run
+        //    and therefore the file is created.
+        // 2. contains task dependency information so that the consumer(s) run after the producer.
+        mainOutput.versionCode.set(versionCodeTask.map { it.versionCodeOutputFile.get().asFile.readText().toInt() })
+        mainOutput.versionName.set("$major.$minor.$patch$versionNameSuffix")
+
+        it.buildConfigFields.put("REPOSITORY_CHANGESET", versionCodeTask.map {
+            BuildConfigField("String", "\"${it.changesetOutputFile.get().asFile.readText()}\"", "Repository changeset")
+        })
+    }
+}