Implement local-first remote sync flow

Makefile

@@ -11,6 +11,11 @@ ANDROID_MIN_SDK ?= 28
 ANDROID_TARGET_SDK ?= 35
 SIGNKEY ?=
 SIGNPASS ?=
+ARCH_PKG_DIR ?= packaging/archlinux/keepassgo-git
+ARCH_PKG_TMPL ?= $(ARCH_PKG_DIR)/PKGBUILD.tmpl
+ARCH_PKGBUILD ?= $(ARCH_PKG_DIR)/PKGBUILD
+ARCH_PKGVER ?= $(shell printf 'r%s.%s' "$$(git rev-list --count HEAD 2>/dev/null || echo 0)" "$$(git rev-parse --short HEAD 2>/dev/null || echo dev)")
+ARCH_REPO_DIR ?= $(CURDIR)
 
 GOGIO_SIGN_FLAGS :=
 ifneq ($(strip $(SIGNKEY)),)
@@ -20,7 +25,7 @@ ifneq ($(strip $(SIGNPASS)),)
 GOGIO_SIGN_FLAGS += -signpass $(SIGNPASS)
 endif
 
-.PHONY: apk
+.PHONY: apk archlinux-pkgbuild
 apk: android/keepassgo-android.jar
 	@test -x "$(JAVA_HOME)/bin/java" || { echo "JAVA_HOME must point to a working JDK install"; exit 1; }
 	@test -d "$(ANDROID_SDK_ROOT)" || { echo "ANDROID_SDK_ROOT must point to an Android SDK install"; exit 1; }
@@ -56,3 +61,10 @@ android/keepassgo-android.jar: $(shell find androidsrc -type f | sort)
 			-d "$$tmpdir" \
 			$$(find androidsrc -name '\''*.java'\'' | sort); \
 		"$(JAVA_HOME)/bin/jar" --create --file "$$(pwd)/android/keepassgo-android.jar" -C "$$tmpdir" .'
+
+archlinux-pkgbuild: $(ARCH_PKG_TMPL) Makefile
+	@mkdir -p "$(ARCH_PKG_DIR)"
+	@sed \
+		-e 's|@PKGVER@|$(ARCH_PKGVER)|g' \
+		-e 's|@REPO_DIR@|$(ARCH_REPO_DIR)|g' \
+		"$(ARCH_PKG_TMPL)" > "$(ARCH_PKGBUILD)"