Make install.sh work if run outside its path

install.sh

@@ -11,7 +11,17 @@
 a2serverVersion="1.9.0"
 a2sScriptURL="https://raw.githubusercontent.com/RasppleII/a2server/master"
 
-# Run the legacy setup script for anything not yet ported
-if [ -e setup/index.txt ]; then
-	source setup/index.txt "$@"
+a2sDevel="$( dirname "${BASH_SOURCE[0]}" )"
+if [[ -f "$a2sDevel/.a2server_source" ]]; then
+	pushd $a2sDevel >/dev/null
+	a2sDevel="$PWD"
+	popd >/dev/null
+else
+	printf "a2server: Cannot find a2server source tree relative to ${BASH_SOURCE[0]}\n\n"
+	exit 1
+fi
+
+# Run the legacy setup script for anything not yet ported
+if [[ -e "${a2sDevel}/setup/index.txt" ]]; then
+	source "${a2sDevel}/setup/index.txt" "$@"
 fi