app version based on git tags

src/pandroid/app/build.gradle.kts

@@ -1,3 +1,5 @@
+import java.lang.ProcessBuilder.Redirect
+
 plugins {
     id("com.android.application")
 }
@@ -10,8 +12,8 @@ android {
         applicationId = "com.panda3ds.pandroid"
         minSdk = 24
         targetSdk = 33
-        versionCode = 1
-        versionName = "1.0"
+        versionCode = getGitVersionCode()
+        versionName = getGitVersionName()
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
 
@@ -54,3 +56,91 @@ dependencies {
     implementation("androidx.constraintlayout:constraintlayout:2.1.4")
     implementation("com.google.code.gson:gson:2.10.1")
 }
+
+/**
+ * Returns the version name based on the current git state
+ * If HEAD is a tag, the tag name is used as the version name
+ * e.g. `1.0.0`
+ * If HEAD is not a tag, the tag name, the branch name and the short commit hash are used
+ * e.g. `1.0.0-master-ab00cd11`
+ */
+fun getGitVersionName(): String {
+    var versionName = "0.0.0"
+
+    try {
+        val process = ProcessBuilder("git", "describe", "--abbrev=0")
+            .directory(project.rootDir)
+            .redirectOutput(Redirect.PIPE)
+            .start()
+        val tag = process.inputStream.bufferedReader().readText().trim()
+        if (!tag.isEmpty())
+            versionName = tag
+
+        versionName += "-" + getGitBranch() + "-" + getGitShortHash()
+    } catch (e: Exception) {
+        logger.quiet("$e: defaulting to dummy version number $versionName")
+    }
+
+    logger.quiet("Version name: $versionName")
+    return versionName
+}
+
+
+/**
+ * Returns the number of commits until the last tag
+ */
+fun getGitVersionCode(): Int {
+    var versionCode = 1
+
+    try {
+        val process = ProcessBuilder("git", "rev-list", "--first-parent", "--count", "--tags")
+            .directory(project.rootDir)
+            .redirectOutput(Redirect.PIPE)
+            .start()
+        val output = process.inputStream.bufferedReader().readText().toInt()
+        versionCode = maxOf(output, versionCode)
+    } catch (e: Exception) {
+        logger.error("$e: defaulting to dummy version code $versionCode")
+    }
+
+    logger.quiet("Version code: $versionCode")
+    return versionCode
+}
+
+/**
+ * Returns the short commit hash
+ */
+fun getGitShortHash(): String {
+    var gitHash = "0"
+
+    try {
+        val process = ProcessBuilder("git", "rev-parse", "--short", "HEAD")
+            .directory(project.rootDir)
+            .redirectOutput(Redirect.PIPE)
+            .start()
+        gitHash = process.inputStream.bufferedReader().readText().trim()
+    } catch (e: Exception) {
+        logger.error("$e: defaulting to dummy build hash $gitHash")
+    }
+
+    return gitHash
+}
+
+/**
+ * Returns the current branch name
+ */
+fun getGitBranch(): String {
+    var branch = "unk"
+
+    try {
+        val process = ProcessBuilder("git", "rev-parse", "--abbrev-ref", "HEAD")
+            .directory(project.rootDir)
+            .redirectOutput(Redirect.PIPE)
+            .start()
+        branch = process.inputStream.bufferedReader().readText().trim()
+    } catch (e: Exception) {
+        logger.error("$e: defaulting to dummy branch $branch")
+    }
+
+    return branch
+}