This package is a first attempt at converting ruby gems to rpm's. Because of the differences between the two packaging schemes, it is impossible to come up with a completely automated way of doing the conversion, but the spec files produced by this package should be good enough for most pure-ruby gems. I wouldn't put too much hope into automating the gem->rpm process for gems with binary code such as database drivers. But even for those, gem2rpm provides a good starting point for the packaging gems as RPM's.
Download the ruby gem or an RPM (TODO: more detail)
Run 'gem2rpm --help' for options
At its simplest, download a gem (let's call it GEM) in its latest version (e.g. 1.2.3):
$ gem fetch GEM
and run gem2rpm above the downloaded file:
$ gem2rpm GEM-1.2.3.gem
You can also use the --fetch flag to fetch the (latest) gem before generating the spec file, achieving the same effect as running 'gem fetch GEM' plus 'gem2rpm GEM-1.2.3.gem':
$ gem2rpm --fetch GEM
This will print an rpm spec file based on the information contained in the gem's spec file. In general, it is necessary to edit the generated spec file because the gem is missing some important information that is customarily provided in rpm's, most notably the license and the changelog.
Rather than editing the generated specfile, edit the template from which the specfile is generated. This will make it easier to update the RPM when a new version of the Gem becomes available.
To support this process, it is recommended to first save the default template somewhere: gem2rpm -T > rubygem-GEM.spec.template
Now, edit the template and then run gem2rpm to generate the spec file using the edited template: gem2rpm -t rubygem-GEM.spec.template > rubygem-GEM.spec
With that, you can now build your RPM as usual. When a new version of the gem becomes available, you should edit the saved template and rerun gem2rpm over it.
The template is a standard erb file; there are two main variables available in the template file:
package - The Gem::Package for the gem spec - The Gem::Specification for the gem (the same as format.spec)
Deprecated:
format - The Gem::Format for the gem. Please note that this is kept just for compatibility reasons, since RubyGems 2.0 removed this class.
A typical source RPM for a gem should consist of three files: the gem file itself, the template for the spec file and the spec file. To ensure that the template will be included in the source RPM, it must be listed as one of the sources in the spec file.
The resulting rpms should follow the naming convention 'rubygem-$GEM' where GEM is the name of the packaged gem. The default template also makes sure that the resulting package provides 'ruby($GEM)', according to general packaging conventions for scripting languages.
Gem has some important limitations that make it next to impossible to fully automate the gem -> rpm conversion process. Amongst them are
Fedora ruby and rubygem packaging guidelines: http://fedoraproject.org/wiki/Packaging/Ruby
Project website https://github.com/lutter/gem2rpm/