I copied all files except dot files (.github and .gitignore), the _examples
folder, and go.mod/go.sum.
At some point we may want to copy the files back to the gocui repo when other
clients (e.g. lazydocker) want to use the newer versions of them.
While we try to keep the view's cursor position in sync with the context state's
selectedLineIdx (at least when pressing up or down), there are enough situations
where the two run out of sync; for example when initially opening the view, or
after staging a hunk, or when scrolling the view using the wheel. While it would
be possible to fix these situations to keep them always in sync, it doesn't seem
worth it, because the view's cursor position isn't really used for anything
else. So we rather special-case the SelectedLine/SelectedLineIdx functions of
ViewDriver to query the context state's selectedLineIdx directly if it is a
patch explorer context.
