As a security engineer I would like Stash to automatically invite me into any new code review in a repo whenever:

• Specific files are modified
• Certain code constructs are removed by the change under review
• Certain code constructs are added by the change under review
• Commit message matches a specified pattern.

We have some functionality in Panopticon which watches a set of files specified per repo. We also match diffs - whether the "removed" patch matches a substring or whether "added" part matches other substrings.

A filename match and a regex on diffs will probably to it. Our somewhat extensive configs are in https://bitbucket.org/atlassian/repo_monitor_configuration/

This function can be a plugin.

(ex-Facebook) Phabricator has a related function - Herald - http://www.phabricator.com/docs/phabricator/article/Herald_User_Guide.html. The whole idea of "actions based on rules" is very nice - at the moment we (SE) need only "invite this user to the review" or, even better, "invite one of these users to the review if none of them are on it already".