[feat] add polkit policy file generation script

The build-polkit-policy.sh script (in the newly added 'scripts' folder) builds a
polkit policy file for swhkd. It has a number of optional arguments to make it
easy to extend and adapt to different use cases. The output path, the swhkd
binary path, and even the custom authentication message and the action id are
configurable.

scripts/build-polkit-policy.sh

@@ -0,0 +1,89 @@
+#!/bin/sh
+
+###############
+# Defaults
+###############
+
+readonly DEFAULT_SWHKD_PATH="/usr/bin/swhkd"
+readonly DEFAULT_POLICY_PATH="com.github.swhkd.pkexec.policy"
+readonly DEFAULT_MESSAGE="Authentication is required to run Simple Wayland Hotkey Daemon"
+readonly DEFAULT_ACTION_ID="com.github.swhkd.pkexec"
+
+###############
+# Init
+###############
+
+print_help() {
+    printf "Usage: build-polkit-policy [OPTIONS]\n\n"
+    printf "Generates a polkit policy file for swhkd.\n\n"
+    printf "Optional Arguments:\n"
+    printf " --policy-path=<path> Path to save the policy file to.\n"
+    printf "                      If set to '-', this tool will output to stdout instead.\n"
+    printf "                      Defaults to '%s'.\n" "${DEFAULT_POLICY_PATH}"
+    printf " --swhkd-path=<path>  Path to the swhkd binary when installed.\n"
+    printf "                      Defaults to '%s'.\n" "${DEFAULT_SWHKD_PATH}"
+    printf " --action-id=<id>     Polkit action id to use.\n"
+    printf "                      Defaults to '%s'.\n" "${DEFAULT_ACTION_ID}"
+    printf " --message=<text>     Custom authentication message.\n"
+    printf "                      Defaults to '%s'\n" "${DEFAULT_MESSAGE}"
+    printf " -h|--help            Show this help.\n"
+}
+
+while [ -n "$1" ]; do
+    case "$1" in
+        --policy-path=*)
+            POLICY_PATH=${1#*=}
+            shift
+            ;;
+        --swhkd-path=*)
+            SWHKD_PATH=${1#*=}
+            shift
+            ;;
+        --action-id=*)
+            ACTION_ID=${1#*=}
+            shift
+            ;;
+        --message=*)
+            MESSAGE=${1#*=}
+            shift
+            ;;
+        -h|--help)
+            print_help
+            exit 0
+            ;;
+        *)
+            printf "Unknown option '%s'. Aborting.\n" "$1"
+            exit 1
+            ;;
+    esac
+done
+
+print_policy() {
+cat << EOF
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE policyconfig PUBLIC "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN" "http://www.freedesktop.org/standards/PolicyKit/1/policyconfig.dtd">
+<policyconfig>
+  <action id="${ACTION_ID}">
+    <message>${MESSAGE}</message>
+    <defaults>
+      <allow_any>no</allow_any>
+      <allow_inactive>no</allow_inactive>
+      <allow_active>yes</allow_active>
+    </defaults>
+    <annotate key="org.freedesktop.policykit.exec.path">${SWHKD_PATH}</annotate>
+  </action>
+</policyconfig>
+EOF
+}
+
+# No local variables in POSIX sh, so just set these globally
+POLICY_PATH="${POLICY_PATH:-${DEFAULT_POLICY_PATH}}"
+SWHKD_PATH="${SWHKD_PATH:-${DEFAULT_SWHKD_PATH}}"
+ACTION_ID="${ACTION_ID:-${DEFAULT_ACTION_ID}}"
+MESSAGE="${MESSAGE:-${DEFAULT_MESSAGE}}"
+
+if [ "${POLICY_PATH}" = "-" ]; then
+    print_policy
+else
+    print_policy > "${POLICY_PATH}"
+fi