scripts/install-lua.sh: init script

Add a script that installs a Lua source archive into the Callisto
source tree. This will ease the pain of transitioning to Lua 5.4.7.

References: https://todo.sr.ht/~jeremy/callisto/8

scripts/install-lua.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env sh
+# usage: scripts/install-lua.sh lua-x.x.x.tar.gz
+# Install a Lua release into the Callisto source tree.
+
+set -e
+
+[ -z "$1" ] && (echo "usage: $0 lua-x.x.x.tar.gz"; exit 1)
+! [ -d external/lua ] && (echo "not in Callisto source tree"; exit 1) || true
+
+# clear out existing Lua sources
+cd external/lua/
+for file in $(ls -A | sed -Ee 's/^(patches|.gitignore)$//'); do
+	rm -fr "$file"
+done
+cd ../../
+
+# install new Lua sources
+luadir="$(tar -tf "$1" | head -n1)"
+rm -rf "$luadir"
+tar -xf "$1"
+ls "$luadir"
+mv "$luadir"/README "$luadir"/src/
+cp -R "$luadir"/src/* external/lua/
+rm -r "$luadir"
+
+# patch the sources
+cd external/lua
+for patch in $(ls patches/); do
+	patch -p0 -i patches/"$patch"
+done
+cd ../../