Use a shell script for creating the OTA zip

* The gradle task breaks on updating the android plugin to 2.2.0,
  so let's just use a shell script to make things easier maintenance
  wise.
diff --git a/create_ota.sh b/create_ota.sh
new file mode 100755
index 0000000..b02a88a
--- /dev/null
+++ b/create_ota.sh
@@ -0,0 +1,84 @@
+#!/bin/bash
+#
+# Script to prepare an update.zip containing F-Droid and the Privileged Extension.
+
+set -e
+
+PROG_DIR=$(dirname $(realpath $0))
+
+TMP_DIR=$(mktemp -d -t fdroidprivext.tmp.XXXXXXXX)
+trap "rm -rf $TMP_DIR" EXIT
+
+function error() {
+	echo "*** ERROR: " $@
+	usage
+}
+
+function usage() {
+	cat << EOFU
+Usage: $0 variant [binaries]
+where:
+ - variant is one of: debug, release
+ - binaries is set for using prebuilt apks,
+   not set by default.
+EOFU
+	exit 1
+}
+
+# Parse input
+VARIANT="$1"
+[[ -z "$VARIANT" ]] && error "Missing variant"
+
+BINARIES="$2"
+
+VERSION=$(grep versionCode=\"\[[:digit:]]\*\" app/src/main/AndroidManifest.xml | cut -d \" -f 2)
+GITVERSION=$(git describe --tags --always)
+
+FDROID_APK=org.fdroid.fdroid_102250.apk
+PRIVEXT_APK=org.fdroid.fdroid.privileged_${VERSION}.apk
+
+# Collect files
+mkdir -p $TMP_DIR/META-INF/com/google/android/
+cp app/src/main/scripts/update-binary $TMP_DIR/META-INF/com/google/android/
+cp app/src/main/scripts/80-fdroid.sh $TMP_DIR/
+
+if [ -z $BINARIES ] ; then
+	$PROG_DIR/gradlew assemble$(echo $VARIANT | tr 'dr' 'DR')
+	if [ $VARIANT == "debug" ]; then
+		cp $PROG_DIR/app/build/outputs/apk/FDroidPrivilegedExtension-${VARIANT}.apk $TMP_DIR/FDroidPrivilegedExtension.apk
+	elif [ -f PROG_DIR/app/build/outputs/apk/FDroidPrivilegedExtension-${VARIANT}-signed.apk ]; then
+		cp PROG_DIR/app/build/outputs/apk/FDroidPrivilegedExtension-${VARIANT}-signed.apk $TMP_DIR/FDroidPrivilegedExtension.apk
+	else
+		cp PROG_DIR/app/build/outputs/apk/FDroidPrivilegedExtension-${VARIANT}-unsigned.apk $TMP_DIR/FDroidPrivilegedExtension.apk
+	fi
+else
+	[ ! -f $TMP_DIR/$PRIVEXT_APK ] && curl -L https://f-droid.org/repo/$PRIVEXT_APK > $TMP_DIR/$PRIVEXT_APK
+	[ ! -f $TMP_DIR/${PRIVEXT_APK}.asc ] && curl -L https://f-droid.org/repo/${PRIVEXT_APK}.asc > $TMP_DIR/${PRIVEXT_APK}.asc
+	gpg --keyring $PROG_DIR/f-droid.org-signing-key.gpg --no-default-keyring --verify $TMP_DIR/${PRIVEXT_APK}.asc
+	rm $TMP_DIR/${PRIVEXT_APK}.asc
+	mv $TMP_DIR/$PRIVEXT_APK $TMP_DIR/FDroidPrivilegedExtension.apk
+fi
+
+# For both
+[ ! -f $TMP_DIR/$FDROID_APK ] && curl -L https://f-droid.org/repo/$FDROID_APK > $TMP_DIR/$FDROID_APK
+[ ! -f $TMP_DIR/${FDROID_APK}.asc ] && curl -L https://f-droid.org/repo/${FDROID_APK}.asc > $TMP_DIR/${FDROID_APK}.asc
+gpg --keyring $PROG_DIR/f-droid.org-signing-key.gpg --no-default-keyring --verify $TMP_DIR/${FDROID_APK}.asc
+rm $TMP_DIR/${FDROID_APK}.asc
+mv $TMP_DIR/$FDROID_APK $TMP_DIR/FDroid.apk
+
+# Make zip
+if [ -z $BINARIES ]; then
+	ZIPBASE=FDroidPrivilegedExtension-${GITVERSION}
+else
+	ZIPBASE=FDroidPrivilegedExtensionFromBinaries-${GITVERSION}
+fi
+if [ $VARIANT == "debug" ]; then
+	ZIP=${ZIPBASE}-debug.zip
+else
+	ZIP=${ZIPBASE}.zip
+fi
+mkdir -p $PROG_DIR/build
+[ -f $PROG_DIR/build/$ZIP ] && rm $PROG_DIR/build/$ZIP
+pushd $TMP_DIR
+zip -r $PROG_DIR/build/$ZIP .
+popd
\ No newline at end of file