$ git worktree list
/path/to/bare-source            (bare)
/path/to/linked-worktree        abcd1234 [master]
/path/to/other-linked-worktree  1234abc  (detached HEAD)

git merge ../master
git pull ../imp_2

git clone -b master <repo> master
cd master

# checking out implementation_1 in ../imp_1
git worktree add ../imp_1 implementation_1

# creating branch implementation_2 at master~2 as you check it out in ../imp2:
git worktree add -b implementation_2 ../imp_2 master~2