nvim: add colorcolumn-workaround for git commits

.config/nvim/lua/coding.lua

@@ -20,5 +20,9 @@ packer.use {
 
 vim.api.nvim_create_autocmd('FileType', {
     pattern = { 'gitcommit', 'gitrebase' },
-    command = 'startinsert | 1',
+    callback = function()
+        -- FIXME: why does the autocmd in settings.lua not set it?
+        vim.wo.colorcolumn = tostring(vim.o.textwidth)
+        vim.cmd([[startinsert | 1]])
+    end
 })