Redmine

We are using trac for some time an looking what redmine provides.
Promising so far...
We have a idea how to deal with related issues etc. and want to discuss
the option of having auto-complete or suggest field for related issues.
The autocomplete fucntion can search in a field of a issues (i.e. #id, subject)
to find the related issue.

A good idea how this can look like is here:

http://www.brandspankingnew.net/specials/ajax_autosuggest/ajax_autosuggest_autocomplete.html