Prevent too many redirects error when home page URL set to external_urll
Many users naively set the home page URL setting to external_url (e.g. https://mydomain.com). When an unauthenticated user signs in, this causes endless redirections. For example, this is occuring:
- Unauthenticated user attempts to access https://mydomain.com/dashboard
- Application redirects to the home page URL: https://mydomain.com
- Repeat step 2
In step 3, ApplicationController should have redirected the user to https://mydomain.com/users/sign_in. Disabling the redirection if home page URL is the same as external_url prevents users from messing up.
- Closes https://github.com/gitlabhq/gitlabhq/issues/8843
- Closes #2057