Extend :Remove to accept bang :Remove!

This patch changes the behaviour `:Remove` to only remove the file,
leaving the current buffer untouched. `:Remove!` now has the old
behaviour of removing the file and the buffer.

lua/commands.lua

@@ -15,9 +15,15 @@ end, { nargs = 1 })
 -- vim.loop.fs_rename
 
 -- :Remove the file associated with the current buffer, then delete the buffer
-vim.api.nvim_create_user_command('Remove', function()
+vim.api.nvim_create_user_command('Remove', function(opts)
   local path = vim.fn.expand('%:p')
-  vim.loop.fs_unlink(path, function(err, success)
+  -- Using opts.bang in the callback can cause a SEGFAULT, instead use it
+  -- before invoking the async unlink to select which callback should be called
+  -- on completion.
+  local callback = nil
+  if opts.bang then
+    -- Invoked as :Remove! so also delete the buffer.
+    callback = function(err, success)
       if success then
         vim.schedule(function()
           vim.api.nvim_buf_delete(vim.api.nvim_get_current_buf(), {})
@@ -25,7 +31,17 @@ vim.api.nvim_create_user_command('Remove', function()
       else
         error(err)
       end
-  end)
-end, {})
+    end
+  else
+    -- Invoked as :Remove so don't delete the buffer.
+    callback = function(err, success)
+      if not success then
+        error(err)
+      end
+    end
+  end
+  -- Actually remove the file using the selecte callback.
+  vim.loop.fs_unlink(path, callback)
+end, { bang = true })
 
 -- TODO: :Move