Support for Gitea merge request commit message pattern

[ylbb5e]

Simple user here.

Gitea merge request commit message look like Merge pull request '{title}' (#{id}) from {source} into {target}. I believe that a regex like ^Merge pull request .* from (.+) into .+$ would allow inferring the source branch name, as with other platforms. Is it possible to configure something like this in the TOML config file? Alternatively, could a regex for Gitea be added to src/settings.rs along with the others?

Thank you for creating and developing nice software.