Redirect to SSL base domain and specific path

Hello,

I'm using the following configuration to redirect connections accessing */admin interface to SSL:

[entryPoints]
  [entryPoints.http]
  address = ":80"
    [entryPoints.http.redirect]
    regex = "http://(.*)/admin"
    replacement = "https://${1}/admin"
  [entryPoints.https]
  address = ":443"
  compress = true
    [entryPoints.https.tls]
      [[entryPoints.https.tls.certificates]]
        certFile = "/etc/ssl/mine/fullchain.pem"
        keyFile = "/etc/ssl/mine/privkey.pem"

I would do do the same for the base URL. I would like to redirect the base URL, e.g. s1.mine.com alongside s1.mine.com/admin to SSL, but avoid forced redirect for every other path.

Any ideas how to achieve the proper redirect?

The following seems to work:

regex = "http://(.*)/($|admin)"
replacement = "https://${1}/${2}"