submodules not getting updated

Hi,

I've got an issue where the git plugin doesn't pull down updated submodules when the folder already exists. The plugin logs that the it pulled the new changes in but checking the hash and a known-changed file prove the update wasn't made. Below is my config:

```
domain.com, www.domain.com {
root /var/www/domains/domain.com/hugo/public
git {
repo https://github.com/barry-smithjr/domain.com.git
path ../
hook $PATH $PASSWORD
clone_args --recurse-submodules
then hugo --gc --minify --destination=/var/www/domains/domain.com/hugo/public
}
cache
gzip
log /var/www/domains/domain.com/logs/access.log

tls {
dns cloudflare
}
}
```