How to group git repositories by keyword/tag

Question

How do you group multiple git repositories by keyword or tag or attribute? Do you have to manage repos in some external tool or is it possible to use a git client to find all repos that have a specific attribute?

For example, Project1 was for client X, it was built for iPad, it included a jQuery plugin, and was an experiment with responsive layouts. Project2 was built for Android and has several other attributes.

In typical project management software, I might create tags and keywords for each project so I could find all the jQuery projects, or all the Android + iPad projects.

Could you do this without the external project management software? Could you do this directly in git, or with an existing git repo manager like GitHub or Bitbucket?

Answer 1

Another alternative for grouping repos together has just been announced (January 31st, 2017; 4 years later after the OP's question): "Introducing Topics".

Topics are labels that create subject-based connections between GitHub repositories and let you explore projects by type, technology, and more.

Click on a topic that interests you to find related repositories.
Adding topics to your repositories will help other users discover your projects, too.

See more at the official documentation page on Topics.
You can:

• add Topics:
  
• search repos by topics: for instance, topic:jekyll.

Answer 2

For github you can use gitrep (external oauth app) which allow you to organize starred repos though tags assigning. It's like del.icio.us but for code.

That's how it looks like:

BTW, the tags on the screenshot were assigned automatically.