Merge branch 'docs/add-private-projects-public-access-note' into 'master'

Add documentation on private projects

Closes #48955

See merge request gitlab-org/gitlab-ce!20446

doc/public_access/public_access.md

@@ -30,6 +30,12 @@ in users.
 Any logged in user will have [Guest](../user/permissions.md) permissions
 on the repository.
 
+### Private projects
+
+Private projects can only be cloned and viewed by project members, and
+they will only appear to project members on the public access directory
+(`https://gitlab.example.com/public`).
+
 ### How to change project visibility
 
 1. Go to your project's **Settings**