scripts: Add update POT files CLI script and wrapper

This can be used to execute TxUtils.update_pot_files() from the CLI. The
GDScript is a SceneTree script passed via Godot's --script CLI option.
The shell script is a wrapper to execute Godot with all the necessary
options. Unlike TxUtils.regenerate_pot(), the editor isn't required, so
everything can happen from _init().

Author: dbnicholson

addons/block_code/README.md

@@ -85,7 +85,9 @@ up to date.
 * If files are added or removed, the list of translatable files needs to be
   updated. This can be done by using the **Add** dialog in the [POT
   Generation][pot-generation] tab. Or you can use the **Project → Tools →
-  Update BlockCode translated files** menu item in the editor.
+  Update BlockCode translated files** menu item in the editor. From the command
+  line, the POT file can be regenerated with the `scripts/update-pot-files.sh`
+  shell script.
 
 * If translatable strings have changed, the POT file needs to be updated. This
   can be done by using the **Generate POT** dialog in the [POT

scripts/update-pot-files.gd

@@ -0,0 +1,11 @@
+## BlockCode update translated files script
+##
+## Use this on the Godot command line with the --script option.
+extends SceneTree
+
+const TxUtils := preload("res://addons/block_code/translation/utils.gd")
+
+
+func _init():
+	TxUtils.update_pot_files()
+	quit()

scripts/update-pot-files.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+# Wrapper script to try to execute the update-pot-files.gd main loop script.
+set -e
+
+SCRIPTDIR=$(dirname "$0")
+PROJDIR=$(dirname "$SCRIPTDIR")
+GODOT_SH="$SCRIPTDIR/godot.sh"
+SCRIPT="$SCRIPTDIR/update-pot-files.gd"
+
+exec "$GODOT_SH" --path "$PROJDIR" --headless --script "$SCRIPT"