release: retain old minSdk artifacts when publishing new releases

AnkiDroid/build.gradle

@@ -256,6 +256,25 @@ android {
 play {
     serviceAccountCredentials.set(file("${homePath}/src/AnkiDroid-GCP-Publish-Credentials.json"))
     track.set('alpha')
+
+    // any time we bump minSdk we want Play Store to retain the old artifacts by version code,
+    // so that they remain available for older devices
+    retain {
+        artifacts.set([
+                20700300L, // (2.7, minSdk 10, universal APK)
+                20804300L, // (2.8.4, minSdk 10, universal APK)
+                21004300L, // (2.10.4, minSdk 15, universal APK)
+                // release-2.14 minSdk 16: missing and not re-publishable, see issue 17791
+                121603300L, // (2.16.3, minSdk 21, ABI armeabi-v7a)
+                221603300L, // (2.16.3, minSdk 21, ABI x86)
+                321603300L, // (2.16.3, minSdk 21, ABI arm64-v8a)
+                421603300L, // (2.16.3, minSdk 21, ABI x86_64)
+                121904300L, // (2.19.4, minSdk 23, ABI armeabi-v7a)
+                221904300L, // (2.19.4, minSdk 23, ABI x86)
+                321904300L, // (2.19.4, minSdk 23, ABI arm64-v8a)
+                421904300L, // (2.19.4, minSdk 23, ABI x86_64)
+        ])
+    }
 }
 
 // Install Git pre-commit hook for Ktlint

gradle/libs.versions.toml

@@ -1,6 +1,13 @@
 [versions]
 compileSdk = "35"
+
+# Changing minSdk means newer AnkiDroid versions will not support older devices.
+# However the Play Store will keep old AnkiDroid versions available for older
+# devices *if* you also change AnkiDroid/build.gradle play { retain {} } block
+# to include the version codes of the last released version for the older
+# minSdk. It is critical to update those version codes when you change this.
 minSdk = "24"  # also in testlib/build.gradle.kts
+
 targetSdk = "34"  # also in  ../robolectricDownloader.gradle
 acra = '5.12.0'
 ktlint = '1.5.0'