Makefile: add uninstall target

Make it easy for users to test versions from a git repository by having
an easy way to uninstall.

Makefile

@@ -47,4 +47,13 @@ install: all
 	install -Dm644 org.postmarketos.mobile_config_firefox.metainfo.xml \
 		"$(DESTDIR)/usr/share/metainfo/org.postmarketos.mobile_config_firefox.metainfo.xml"
 
-.PHONY: all clean install
+uninstall:
+	src/prepare_uninstall.sh "$(FIREFOX_DIR)" "$(DESTDIR)"
+	rm -fv "$(DESTDIR)/$(FIREFOX_CONFIG_DIR)/policies/policies.json"
+	rm -fv "$(DESTDIR)/$(FIREFOX_DIR)/defaults/pref/mobile-config-prefs.js"
+	rm -fv "$(DESTDIR)/$(FIREFOX_DIR)/mobile-config-autoconfig.js"
+	rm -rfv "$(DESTDIR)/etc/mobile-config-firefox"
+	rm -fv "$(DESTDIR)/usr/share/metainfo/org.postmarketos.mobile_config_firefox.metainfo.xml"
+
+
+.PHONY: all clean install uninstall

src/prepare_uninstall.sh

+#!/bin/sh -e
+FIREFOX_DIR="$1"
+DESTDIR="$2"
+
+echo
+
+if [ -z "$DESTDIR" ] && [ "$(id -u)" != 0 ]; then
+	echo "ERROR: run 'make uninstall' as root"
+	echo
+	echo "For example:"
+	echo "$ sudo make FIREFOX_DIR=$FIREFOX_DIR uninstall"
+	echo
+	exit 1
+fi
+
+echo "You are about to delete some files and directories, where you may"
+echo "have other firefox customizations than mobile-config-firefox."
+echo "Check the Makefile if unsure."
+echo
+echo "If you want to go back to your distribution's version of"
+echo "mobile-config-firefox, make sure to reinstall the package"
+echo "afterwards with the package manager (apk, apt, pacman, ...)."
+echo
+echo -n "Do you really want to uninstall mobile-config-firefox? [y/N] "
+
+read answer
+
+case "$answer" in
+	[yY])
+		exit 0;;
+	*)
+		exit 1;;
+esac