Re-enable proguard for release builds

It can be disabled for stables if it's not reliable.

Also enabled for debugging so that bugs don't slip into release builds.

.gitignore

@@ -45,6 +45,3 @@ out
 # Imported libs
 extern/*/libs/
 extern/*/*/libs/
-
-# We don't use proguard anywhere
-proguard-project.txt

F-Droid/build.gradle

@@ -153,8 +153,9 @@ android {
 
     buildTypes {
         all {
-            minifyEnabled false
+            minifyEnabled true
-            shrinkResources false // requires minify (proguard)
+            shrinkResources true
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
         debug {
             debuggable true

F-Droid/proguard-rules.pro

@@ -0,0 +1,39 @@
+-dontobfuscate
+-dontoptimize
+-keepattributes SourceFile,LineNumberTable,Exceptions
+-keep class org.fdroid.fdroid.** {*;}
+-dontskipnonpubliclibraryclassmembers
+-dontwarn android.test.**
+-dontwarn com.android.support.test.**
+
+-dontwarn javax.naming.**
+-dontnote android.support.**
+-dontnote **ILicensingService
+
+# The nature of the Java security suite implementations are that they use a
+# lot of reflection to instantiate classes. The end result is that proguard
+# excludes classes which may be required, depending on the security algorithms
+# required by certain certificates.
+#   Reference: https://gitlab.com/fdroid/fdroidclient/issues/88
+-keep class org.spongycastle.crypto.* {*;}
+-keep class org.spongycastle.crypto.digests.* {*;}
+-keep class org.spongycastle.crypto.encodings.* {*;}
+-keep class org.spongycastle.crypto.engines.* {*;}
+-keep class org.spongycastle.crypto.macs.* {*;}
+-keep class org.spongycastle.crypto.modes.* {*;}
+-keep class org.spongycastle.crypto.paddings.* {*;}
+-keep class org.spongycastle.crypto.params.* {*;}
+-keep class org.spongycastle.crypto.prng.* {*;}
+-keep class org.spongycastle.crypto.signers.* {*;}
+
+-keep class org.spongycastle.jcajce.provider.digest.** {*;}
+-keep class org.spongycastle.jcajce.provider.keystore.** {*;}
+-keep class org.spongycastle.jcajce.provider.symmetric.** {*;}
+-keep class org.spongycastle.jcajce.spec.* {*;}
+-keep class org.spongycastle.jce.** {*;}
+
+# This keeps class members used for SystemInstaller IPC.
+#   Reference: https://gitlab.com/fdroid/fdroidclient/issues/79
+-keepclassmembers class * implements android.os.IInterface {
+    public *;
+}