Fail the the finish_release.sh script if the tag already exists locally

Motivation:

We should fail the script if the tag already exists locally to ensure we really deploy the right code

Modifications:

Check if the tag already exists and if so print an error and exit

Result:

No risks to deploy wrong code as part of the release

scripts/finish_release.sh

@@ -15,6 +15,11 @@ fi
 
 BRANCH=$(git branch --show-current)
 
+if git tag | grep -q "$2" ; then
+    echo "Tag $2 already exists"
+    exit 1
+fi
+
 git fetch
 git checkout "$2"