Allow to query against empty search string

[gennaro-tedesco]

Following this discussion it can be useful to allow the user to skip the prompt for repository name and query against topic and language only.

The idea is to implement a new flag, say -E, such that whenever such flag is passed, the query string defaults to empty name and we search against the rest of the flags only. Whilst this may result in very wide searches and therefore longer response times, it does allow for nice use cases of statistics and repository lists.

• PR
• Wiki examples

[gennaro-tedesco]

Merged