Currently all the 'History' links in the SCM browse go to a URL like https://sourceforge.net/p/allura/git/ci/0298d85091dd970b0c6d57c914e43643b604a6a8/log/ which shows the revisions starting at the given commit. There should be a way to view revisions limited to a specified directory or file. E.g. URL might be something like https://sourceforge.net/p/allura/git/ci/0298d85091dd970b0c6d57c914e43643b604a6a8/log/ForgeBlog/forgeblog/tests/ This needs to be implemented for Git, Hg, and SVN.
Then, change the History links so that when you're browsing a tree or file, the link goes to the /log/ URL containing the file/folder path.