feat: add patch series, build scripts and release automation

scripts/latest-upstream.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+# Print the newest Modrinth App release tag upstream has published.
+#
+# With --write, also store it in upstream.txt. Exits with status 0 either way;
+# compare the output with upstream.txt to find out whether anything moved.
+
+. "$(dirname "${BASH_SOURCE[0]}")/common.sh"
+
+latest="$(
+	git ls-remote --tags --refs "$UPSTREAM_REPO" 'v*' |
+		sed 's#.*refs/tags/##' |
+		grep -E '^v[0-9]+\.[0-9]+\.[0-9]+$' |
+		sort -V |
+		tail -1
+)"
+
+[ -n "$latest" ] || die "Could not determine the latest upstream release tag"
+
+if [ "${1:-}" = --write ]; then
+	printf '%s\n' "$latest" >"$REPO_ROOT/upstream.txt"
+fi
+
+printf '%s\n' "$latest"