rsend: push phone folders to a home SSH host over rsync

A small Android app for one-way folder backup, a KISS alternative to
Syncthing. It bundles rsync (built from pinned source via the NDK) and
a pure-Go SSH transport, both shipped in the APK as lib*.so and run from
the native library directory.

rsend pins the host key, stores the ed25519 identity Keystore-encrypted,
pushes each folder additively or as a mirror, and runs on demand or on a
WiFi-only schedule. The build is self-contained and reproducible: make
setup provisions the toolchain, make builds rsync, rsh, and the APK.

1 files changed, 73 insertions, 0 deletions

diff --git a/ci/setup-toolchain.sh b/ci/setup-toolchain.sh
new file mode 100755
index 0000000..c832708
--- /dev/null
+++ b/ci/setup-toolchain.sh
@@ -0,0 +1,73 @@
+#!/bin/sh
+# Provision the pinned Android build toolchain into TOOLCHAIN_DIR (default
+# $HOME/toolchains): JDK 17, Android cmdline-tools, SDK platform, build-tools,
+# NDK, and Gradle. Idempotent: re-running only fills what is missing. Writes an
+# env.sh to source before building. This is what CI runs to get a build host.
+set -eu
+
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+. "$root/versions"
+
+dir=${TOOLCHAIN_DIR:-$HOME/toolchains}
+sdk="$dir/android-sdk"
+mkdir -p "$dir/dl"
+
+# JDK 17 (Temurin).
+if [ ! -x "$dir/jdk17/bin/java" ]; then
+	echo "setup: JDK $JDK_VERSION"
+	curl -fsSL "https://api.adoptium.net/v3/binary/latest/${JDK_VERSION}/ga/linux/x64/jdk/hotspot/normal/eclipse" -o "$dir/dl/jdk.tar.gz"
+	mkdir -p "$dir/jdk17"
+	tar xzf "$dir/dl/jdk.tar.gz" -C "$dir/jdk17" --strip-components=1
+fi
+export JAVA_HOME="$dir/jdk17"
+export PATH="$JAVA_HOME/bin:$PATH"
+
+# Android cmdline-tools.
+if [ ! -x "$sdk/cmdline-tools/latest/bin/sdkmanager" ]; then
+	echo "setup: cmdline-tools $ANDROID_CMDLINE_TOOLS"
+	curl -fsSL "https://dl.google.com/android/repository/commandlinetools-linux-${ANDROID_CMDLINE_TOOLS}_latest.zip" -o "$dir/dl/clt.zip"
+	rm -rf "$dir/dl/clt"
+	python3 -m zipfile -e "$dir/dl/clt.zip" "$dir/dl/clt"
+	mkdir -p "$sdk/cmdline-tools"
+	rm -rf "$sdk/cmdline-tools/latest"
+	mv "$dir/dl/clt/cmdline-tools" "$sdk/cmdline-tools/latest"
+	chmod +x "$sdk/cmdline-tools/latest/bin/"*
+fi
+
+# SDK packages.
+echo "setup: sdk packages"
+yes | "$sdk/cmdline-tools/latest/bin/sdkmanager" --licenses >/dev/null 2>&1 || true
+"$sdk/cmdline-tools/latest/bin/sdkmanager" \
+	"platform-tools" \
+	"platforms;android-${ANDROID_PLATFORM}" \
+	"build-tools;${ANDROID_BUILD_TOOLS}" \
+	"ndk;${ANDROID_NDK}" >/dev/null
+
+# Gradle.
+if [ ! -x "$dir/gradle-${GRADLE_VERSION}/bin/gradle" ]; then
+	echo "setup: Gradle $GRADLE_VERSION"
+	curl -fsSL "https://services.gradle.org/distributions/gradle-${GRADLE_VERSION}-bin.zip" -o "$dir/dl/gradle.zip"
+	python3 -m zipfile -e "$dir/dl/gradle.zip" "$dir"
+	chmod +x "$dir/gradle-${GRADLE_VERSION}/bin/gradle"
+fi
+
+# Go (pinned; builds rsh).
+if [ ! -x "$dir/go/bin/go" ]; then
+	echo "setup: Go $GO_VERSION"
+	curl -fsSL "https://go.dev/dl/go${GO_VERSION}.linux-amd64.tar.gz" -o "$dir/dl/go.tar.gz"
+	rm -rf "$dir/go"
+	tar xzf "$dir/dl/go.tar.gz" -C "$dir"
+fi
+
+# Emit the env to source before building.
+cat > "$dir/env.sh" <<EOF
+export JAVA_HOME="$dir/jdk17"
+export GOROOT="$dir/go"
+export ANDROID_HOME="$sdk"
+export ANDROID_SDK_ROOT="$sdk"
+export ANDROID_NDK_HOME="$sdk/ndk/${ANDROID_NDK}"
+export GRADLE_HOME="$dir/gradle-${GRADLE_VERSION}"
+export PATH="\$JAVA_HOME/bin:$dir/go/bin:\$GRADLE_HOME/bin:$sdk/cmdline-tools/latest/bin:$sdk/platform-tools:\$PATH"
+EOF
+
+echo "setup: done; source $dir/env.sh"