On Tue, Jan 26, 2016 at 06:44:41PM +0700, Nguyễn Thái Ngọc Duy wrote:

Worktree v1 may have different .git file split than v0. Add support
code to change common file list based on extensions.worktree. The list
for now is identical to v0.

In the end this turned out to be needed only for "common"
which is not strictly necessary, as Junio pointed out, and
anyway could be done for v0 as well because "common" is not
used to be used before. So probably it is not needed at all.