android: Bring back git hash version name

src/android/app/build.gradle

@@ -33,6 +33,7 @@ android {
         minSdkVersion 26
         targetSdkVersion 28
         versionCode autoVersion
+        versionName getVersion()
         ndk.abiFilters abiFilter
     }
 
@@ -122,3 +123,17 @@ dependencies {
 
     implementation 'com.android.billingclient:billing:2.2.0'
 }
+
+def getVersion() {
+    def versionName = '0.0'
+
+    try {
+        versionName = 'git describe --always --long'.execute([], project.rootDir).text
+                .trim()
+                .replaceAll(/(-0)?-[^-]+$/, "")
+    } catch (Exception e) {
+        logger.error('Cannot find git, defaulting to dummy version number')
+    }
+
+    return versionName
+}