Tested on Gitea 1.8.0

Currently the status if a PR has conflicts to the target branch is not updated when there are new commits pushed to the target branch.

Scenario:

I branch off from master to implement a feature. When the feature is implemented, I first want to merge it into a QA branch via PR.
If master and QA have diverged too much (e.g. a lot of testing at the moment), I get conflicts from feature to QA, which is expected.

However, if I then merge master into QA the conflicts might be resolved.
When I now look into the PR, it still says it has the same conflicts as before, which led me to the conclusion that the mergeability is not evaluated again if there are updates to the target branch.

I think this would be a great QoL feature