add The Big Benchmark as a shell script

data/.gitignore

@@ -1,2 +1,3 @@
 xonotic-*.pk3dir
 *.pk3
+benchmark.log

the-big-benchmark.sh

@@ -0,0 +1,50 @@
+#!/bin/sh
+
+set -e
+
+echo "The Big Benchmark"
+echo " ================="
+echo
+echo "WARNING: running this script will destroy ANY local changes you"
+echo "might have on the repository."
+echo
+echo "Are you absolutely sure you want to run this?"
+echo
+while :; do
+	echo -n "y/n: "
+	read -r yesno
+	case "$yesno" in
+		y)
+			break
+			;;
+		n)
+			echo "Aborted."
+			exit 1
+			;;
+	esac
+done
+
+set -x
+./all clean --reclone
+./all compile -r
+./all run -nohome -benchmarkruns 3 -benchmark demos/the-big-keybench.dem +//div0-stable
+./all clean --reclone
+(
+	cd darkplaces
+	git checkout master || git checkout -t origin/master || exit 1
+)
+./all compile -r
+./all run -nohome -benchmarkruns 3 -benchmark demos/the-big-keybench.dem +//master
+./all clean --reclone
+
+echo
+echo "Please provide the the following info to the Xonotic developers:"
+echo " - CPU speed"
+echo " - memory size"
+echo " - graphics card (which vendor, which model)"
+echo " - operating system (including whether it is 32bit or 64bit)"
+echo " - graphics driver version"
+echo " - the following info:"
+tail -n 6 data/benchmark.log
+echo
+echo "Thank you"