I'd like to create a hotkey to insert the current branch name directly in insert mode with the hotkey <C-b>. I use the plugin gitsigns which has a variable vim.b.gitsigns_head containing the current branch but I can't seem to find a way to input it. I figured I need to add something like

vim.keymap.set('i', '<C-b>', vim.b.gitsigns_head)

but I can't find any way to reference and print the variable.