I have this binding to start a code review in neovim directly from the selected commit in tig:

bind main v !>nvim +'DiffviewOpen %(commit)~1..%(head)' 

Thing is .. that only works if the branch I want to review is currently checked out or if I use tig -> view-refs, select the branch and commit and then use the keybind.

If I start tig with a branch directly, e.g. tig origin/some/branch and select a commit, the %(head) variable contains the wrong commit (the one of the currently checked out branch, not the branch I called tig with).

Edit: I also tried %(branch) and %(refname) but they wont work either.