Revert "Revert "Merge branch 'git_hook_messages'""

This reverts commit f8453da5868dd7a23d0f2f3da7a45e33c441d1db.
Merge branch 'git_messages' into 'master'

Better git hook messages

DZ already merged it but we had to revert it because of lack of time to deploy to dev.

See merge request !48
Add missing 'require_relative' in gitlab_net.rb

Without this 'require' statement, you get the following error:

```
$ git ls-remote origin
/home/git/gitlab-shell/lib/gitlab_net.rb:30:in `check_access':
uninitialized constant GitlabNet::GitAccessStatus (NameError)
  from /home/git/gitlab-shell/lib/gitlab_shell.rb:63:in `validate_access'
  from /home/git/gitlab-shell/lib/gitlab_shell.rb:24:in `exec'
  from /home/git/gitlab-shell/bin/gitlab-shell:16:in `<main>'
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
```
Merge branch 'require_in_gitlab_net' into 'master'

Add missing 'require_relative' in gitlab_net.rb

Prevent 'uninitialized constant GitlabNet::GitAccessStatus'.

See merge request !49