When comparing files, and updating a source code repository, I like to use vimdiff. To copy changes made from one file to the other, I usually use a key sequence like this:-
Shift + V (select line)
k or j; { or }; Up or down arrow keys (select more lines)
y (copy selected lines)
Ctrl + w, left/right arrow (move to other pane)
p (paste lines)
Vim, being the master of keyboard shortcuts, should surely have an easier way of performing this same task. Is there one? What do you use to manually update source-code changes?