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

@@ -15,17 +15,33 @@ 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)
-    if success then
-      vim.schedule(function()
-        vim.api.nvim_buf_delete(vim.api.nvim_get_current_buf(), {})
-      end)
-    else
-      error(err)
+  -- 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(), {})
+        end)
+      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