(Based on PSA in https://groups.google.com/a/chromium.org/d/msg/chromium-dev/rXYPzakFy0E/WafliQVuaWoJ)
Bugdroid  has recently updated the set of "BUG=" formats that it accepts. The most visible change is that the "BUG=project:n" format is more universally  accepted, so you may already have noticed more bug updates coming in for commits that were previously ignored. The matching rules have also been cleaned up a bit, so they should no longer produce some common false-positives, like treating 'disable_nacl=1' as a nacl bug.
Below is the specification of officially supported formats, based on the previous patterns and observed usage (regression tested against thousands of actual commit messages). The pattern-matching rules are still fairly loose, so some not-quite-right formats, like "BUG====n", may work, but are not guaranteed. Please let me know if you encounter any formats that you expect to work but which don't.
Matches issue 'n' in the default issue tracker for the repository (e.g. skia tracker for skia repos, chromium tracker for chromium and blink, etc.).
Matches issue 'n' in the issue tracker for 'project'.
BUG=<Issue Tracker URL>
A direct link to an issue tracker page matches that issue.
- The keywords 'BUG' and 'ISSUE' are interchangeable in all formats.
- 'n' can be a comma-delimited list of bug #'s.
- If 'n' is a list, all items belong to the most recent project specifier preceding the list, e.g.:
is equivalent to:
- Multiple bug lines may appear in the commit message.
- Project/URL specification only works for configured projects .
 Where "universal" is defined as the set of known projects  configured for each repo. For instance, a bug in the blink repo can specify "BUG=chromium:n", but not "BUG=skia:n", because that just seems unlikely. If you encounter a case where one project should be able to create bugs for another, but can't, let me know.
 "Known projects" are the issue trackers which have been configured to allow read/write access for the bugdroid account, currently chromium, nativeclient, webrtc, v8, and skia.