The wiki syntax commit:repo_a used to link hash-named changesets doesn't work if repo identifier has underscore symbol.

Maybe in this code https://github.com/redmine/redmine/blob/master/app/helpers/application_helper.rb#L751 used wrong regular expression.

          when 'commit', 'source', 'export'
            if project
              repository = nil
              if name =~ %r{^(([a-z0-9\-]+)\|)(.+)$}
                repo_prefix, repo_identifier, name = $1, $2, $3
                repository = project.repositories.detect {|repo| repo.identifier == repo_identifier}
              else
                repository = project.repository
              end