benchmark script: make sure a master branch exists

build-and-benchmark-py-project.sh

@@ -30,6 +30,7 @@ if [[ ! -z "$CI" ]]; then
   rm -rf .asv/env
   # Fetch the master branch as git repository in gitlab ci env doesn't have it.
   git fetch origin master
+  git checkout -t origin/master
 fi
 
 if [[ ! -f ~/.asv-machine.json ]]; then