Fix changing directory.

pull-and-update.sh

@@ -2,7 +2,7 @@
 set -e
 
 # https://stackoverflow.com/a/1482133/270712
-MYDIR=dirname -- "$( readlink -f -- "$0"; )";
+MYDIR=`dirname -- "$( readlink -f -- "$0"; )";`
 pushd "$MYDIR"
 git pull
 docker compose up build