arti-bench.sh: Handle the case where CHUTNEY_PATH is set.

Previously, this case would cause arti-bench to hang forever, trying
to bootstrap against one network while another network was running.

tests/chutney/arti-bench.sh

@@ -6,14 +6,38 @@ if [ -z "$RUST_LOG" ]; then
     export RUST_LOG=info
 fi
 
-target="chutney/networks/basic"
+target="networks/basic"
 cd "$(git rev-parse --show-toplevel)"
-[ -d chutney ] || git clone https://gitlab.torproject.org/tpo/core/chutney
-./chutney/chutney configure "$target"
-./chutney/chutney start "$target"
-CHUTNEY_START_TIME=180 ./chutney/chutney wait_for_bootstrap "$target"
-./chutney/chutney verify "$target"
 
-cargo run -p arti-bench --release -- -c chutney/net/nodes/arti.toml "$@"
+# TODO: Much of the setup logic below is boilerplate.  Maybe the
+# common parts of this script and setup.sh/teardown.sh should be
+# extracted.
+if [ -z "${CHUTNEY_PATH}" ]; then
+    # CHUTNEY_PATH isn't set; try cloning or updating a local chutney.
+    if [ -d chutney ]; then
+	(cd ./chutney && git pull)
+    else
+	git clone https://gitlab.torproject.org/tpo/core/chutney
+    fi
+    CHUTNEY_PATH="$(pwd)/chutney"
+    export CHUTNEY_PATH
+else
+    # CHUTNEY_PATH is set; tell the user so.
+    echo "CHUTNEY_PATH is ${CHUTNEY_PATH}; using your local copy of chutney."
+fi
+
+if [ ! -e "${CHUTNEY_PATH}/${target}" ]; then
+    echo "Target network description ${CHUTNEY_PATH}/${target} not found."
+    exit 1
+fi
+
+"${CHUTNEY_PATH}/chutney" configure "${CHUTNEY_PATH}/$target"
+"${CHUTNEY_PATH}/chutney" start "${CHUTNEY_PATH}/$target"
+CHUTNEY_START_TIME=180 "${CHUTNEY_PATH}"/chutney wait_for_bootstrap "${CHUTNEY_PATH}/$target"
+"${CHUTNEY_PATH}"/chutney verify "${CHUTNEY_PATH}/$target"
+# TODO (end of boilerplate)
+
+cargo run -p arti-bench --release -- -c "${CHUTNEY_PATH}/net/nodes/arti.toml" "$@"
+
+"${CHUTNEY_PATH}"/chutney stop "${CHUTNEY_PATH}/$target"
 
-./chutney/chutney stop "$target"