Versions file not updated for RC-releases

[sudoremo]

Describe the problem as clearly as you can

• Running gem generate_index -d … --update does not include new Gems with RC-versions (e.g. 1.0.0.rc0).
• Running with --update, in contrast to omitting the flag, creates an additional line for each new Gem version instead of altering the existing line. This may not be a bug though.

Did you try upgrading RubyGems?

Yes.

Post steps to reproduce the problem

I have added a new unit test in this fork branch.

Which command did you run?

gem generate_index -d … --update

What were you expecting to happen?

Pre-releases should also be added to the index. Otherwise, they cannot be installed.

What actually happened?

Pre-releases are not added to the index / versions file.