expand commit feed view

[mpdehaan]

the commit feed view is already pretty good, and allows for filtering commits by filename, path, and extension, and shows authors, and links to author stats and so on... but we can also make it better.

We should be able to get the full commit subject if we modify the scanner to collect this, but we should ALSO be able to click on the commit and get the file changes - at least the list of them - that were part of that commit.

[mpdehaan]

also we have the working tree checked out locally ALREADY, so we are able to allow commit browsing from within the app.

This could work just by opening the commit text in a new tab.