Complete filenames which are indicated by %*

This is based on the cmp_cmdline pr that iteratee
It will offer completions for % and %:* as well as # and #:* in cmdline

lua/cmp_cmdline/init.lua

@@ -77,7 +77,7 @@ local definitions = {
     regex = [=[[^[:blank:]]*$]=],
     kind = cmp.lsp.CompletionItemKind.Variable,
     isIncomplete = true,
-    exec = function(option, arglead, cmdline, force)
+    exec = function(option, arglead, cmdline, force, cursorline)
       -- Ignore range only cmdline. (e.g.: 4, '<,'>)
       if not force and ONLY_RANGE_REGEX:match_str(cmdline) then
         return {}
@@ -127,44 +127,49 @@ local definitions = {
 
       local items = {}
       local escaped = cmdline:gsub([[\\]], [[\\\\]]);
-      local is_magic_file = false
       local input_start = string.sub(fixed_input, 1, 1)
-      if input_start == '%' then
-        is_magic_file = true
-      elseif input_start == '#' then
-        is_magic_file = true
-      end
-      for _, word_or_item in ipairs(vim.fn.getcompletion(escaped, 'cmdline')) do
-        local word = type(word_or_item) == 'string' and word_or_item or word_or_item.word
-        local item = { label = word }
-        table.insert(items, item)
-        if is_option_name_completion and is_boolean_option(word) then
-          table.insert(items, vim.tbl_deep_extend('force', {}, item, {
-            label = 'no' .. word,
-            filterText = word,
-          }))
+      local is_magic_file = (#arglead ~= 1 and (input_start == '%' or input_start == '#'))
+      if is_magic_file then
+        for _, word_or_item in ipairs(vim.fn.getcompletion(arglead, 'file')) do
+          local word = type(word_or_item) == 'string' and word_or_item or word_or_item.word
+          local item = { label = word, ismagic=true }
+          table.insert(items, item)
+        end
+      else
+        for _, word_or_item in ipairs(vim.fn.getcompletion(escaped, 'cmdline')) do
+          local word = type(word_or_item) == 'string' and word_or_item or word_or_item.word
+          local item = { label = word }
+          table.insert(items, item)
+          if is_option_name_completion and is_boolean_option(word) then
+            table.insert(items, vim.tbl_deep_extend('force', {}, item, {
+              label = 'no' .. word,
+              filterText = word,
+            }))
+          end
         end
       end
       for _, item in ipairs(items) do
         if not is_magic_file and not string.find(item.label, fixed_input, 1, true) then
           item.label = fixed_input .. item.label
+        end
         if is_magic_file then
-          local replace_range = {
-            start = {
-              line = 0,
-              character = #cmdline - #fixed_input - 1
-            },
-            ['end'] = {
-              line = 0,
-              character = #cmdline - 1
-            }
-          }
           item.textEdit = {
-            replace = replace_range,
-            range = replace_range,
+            -- replace = replace_range,
+            range = {
+              start = {
+                line = cursorline,
+                character = #cmdline - #arglead - 1
+              },
+              ['end'] = {
+                line = cursorline,
+                character = #cmdline - 1
+              }
+            },
             newText = item.label
           }
-          item.label = fixed_input .. item.label
+          item.insert_text = item.label
+          item.label = item.label
+          item.filterText = arglead
         end
       end
       return items
@@ -206,7 +211,8 @@ source.complete = function(self, params, callback)
         vim.tbl_deep_extend('keep', params.option or {}, DEFAULT_OPTION),
         string.sub(params.context.cursor_before_line, s + 1),
         params.context.cursor_before_line,
-        params.context:get_reason() == cmp.ContextReason.Manual
+        params.context:get_reason() == cmp.ContextReason.Manual,
+        params.context.cursor.line
       )
       kind = def.kind
       isIncomplete = def.isIncomplete