BitBucket allows a user to create a fork (or branch) of a repository and request that it be pulled into the master branch. Comments can be made on the pull request, and the discussion of the change will then be on the BitBucket website, rather than in TRAC. Pull requests are more convenient than patches, as there is no need to manually download and apply patch files, and there is a clear audit trail of what was reviewed and when. However, since not all the ET repositories are in BitBucket, this would lead to fragmentation of the review process, with some changes being discussed in TRAC and some in BitBucket.
(See the discussion at http://lists.einsteintoolkit.org/pipermail/users/2014-October/003816.html regarding notifications of pull requests.)