I'm not sure what I did wrong but your mapping didn't work for me on Neovim - it either immediately closed the terminal or didn't know what <bar> means.
Eventually I moved to https://github.com/codeindulgence/vim-tig which does the same via `:Tig` and `:Tig!`.
I added those mappings to achieve something similar:
nnoremap <leader>gb :Tig! blame<cr>
nnoremap <leader>g0 :Tig! status<CR>