This adds a context menu item to the diff viewer pane that calls git
gui blame, focusing it on the clicked line. In case of combined
diffs, it also automatically deduces which parent is to be blamed.
Lines added by the diff are blamed on the current commit itself.
The context menu itself is added by this patch. It would be possible
to add the commands from the flist menu to it.
Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com> Signed-off-by: Paul Mackerras <paulus@samba.org>