md pandoc call turned into script

scripts/md-preamble.tex

+\usepackage{fancyhdr}
+\pagestyle{fancy}
+\fancyhead{}
+\fancyhead[L]{CURRENTCOMMIT}
 \AtBeginDocument{\renewcommand{\setminus}{\mathbin{\backslash}}}

scripts/pandoc-call.sh

+#! /usr/bin/env bash
+mkdir -p .maindir/out
+cp .maindir/scripts/md-preamble.tex .maindir/out/md-preamble-orig.tex
+sed -i 's#CURRENTCOMMIT#'$(git rev-parse --short HEAD)'#' .maindir/scripts/md-preamble.tex
+pandoc --pdf-engine lualatex --lua-filter .maindir/scripts/pandoc-gitlab-math.lua --include-in-header=.maindir/scripts/md-preamble.tex' "$1" -o "${2:-~/Desktop/pandoc.pdf}"
+cp .maindir/out/md-preamble-orig.tex .maindir/scripts/md-preamble.tex