tests: add maxlen.bash helper

Simple script that finds out the maximum supported filename
length.

tests/maxlen.bash

@@ -0,0 +1,18 @@
+#!/bin/bash -eu
+#
+# Find out the maximum supported filename length and print it.
+#
+# Part of the gocryptfs test suite
+# https://nuetzlich.net/gocryptfs/
+
+NAME="maxlen."
+LEN=7
+
+while [ $LEN -le 10000 ]; do
+	touch $NAME 2> /dev/null || break
+	rm $NAME
+	NAME="${NAME}x"
+	let LEN=LEN+1
+done
+
+echo $LEN