Several posts on the forum are about the need of mirroring issues, ie auto updating the status of related issue.
This is an attempt to achieve this result by creating a new relation (two in fact...) called mirror.

The drawback is that callbacks are not properly handled : these patch are not a finished product.

Provided patchs are for the 2.3.0 version, but can easily be transposed for the 2.4 or 2.5 series.
Files to be patched : app/models/issue.rb
app/models/issue_relation.rb
config/locales/fr.yml (ok, for french people....)