meta-info updates

README.md

@@ -16,3 +16,12 @@ directly from git. The usage is something like this (inside .spec file):
 To make it work, the included macro _must be appended_ to either `~/.rpmmacros` or 
 one of the site macro files (see `man rpmbuild`). (If rpmbuild ever handles a reasonable
 method of extension or directory-based includes, that requirement will change.)
+
+For public repositories, no additional effort is required, provided the URL works
+(you can test with `curl` or `wget` or a web browser). For repositories that are private, 
+an access token is required. Set your token inside the environment variable `PRIVATE_TOKEN`
+and that token will be passed along as an HTTP header `PRIVATE-TOKEN`, with a `-` instead of 
+`_` (underscore).
+
+This has been tested with a gitlab-provided repository, running v3 of the API. 
+