Add delta install script

dot_local/bin/executable_install-delta

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# shellcheck disable=SC1091
+source "${XDG_DATA_HOME}/buddy-up/includes/utils.sh"
+
+APP="delta"
+VERSION=${VERSION:-0.16.5}
+DEST=${XDG_DATA_HOME}/apps/releases/${APP}
+
+main() (
+	URL=https://github.com/dandavison/delta/releases/download/${VERSION}/delta-${VERSION}-$(uname -m)-$(get_os).tar.gz
+	extract_tarball "${URL}" "${DEST}/${VERSION}" "--strip-component 1"
+	set_current_link "${DEST}" "${VERSION}"
+	set_link "${XDG_BIN_HOME}/${APP}" "${DEST}" "${APP}"
+)
+
+function get_os () {
+	case $(uname -s) in
+		Linux*)     echo unknown-linux-gnu;;
+		Darwin*)    echo apple-darwin;;
+		*)          >&2 echo "unsupported os: $(uname -s)"; exit 1;;
+	esac
+}
+
+main "${@}"