Some ideas how the annotation bar could be enhanced:
1) add action "Show Annotations for Rev" - there's already Show Ann for Prev, but that opens the file in rev previous to the selected. So opening the file in the selected rev (as is possible from Show History) directly on the *selected line* could be an improvement
2) Show Ann for Prev could jump to a corresponding line (guess the line) or the start of a block (if the line was added in the current rev)
3) Bar could open a view where you could jump between revisions and quickly see the context of the selected line in history:
3 A) move across history and always jump on the fixed line number - this is useful in exception evaluating: you have a line number but don't know the exact revision number, so you want to quickly find a relevant revision
3 B) modified 2) scenario, just not opening the whole file in editor but quickly display it in a popup window view. Useful when you want to overview how the context of the current line evolved

TODO: need to describe the scenarios in detail