Add --cxml flag (#16)

Refs #15

---------

Co-authored-by: Simon Willison <swillison@gmail.com>

tests/test_files_to_prompt.py

@@ -1,5 +1,7 @@
 import os
+
 from click.testing import CliRunner
+
 from files_to_prompt.cli import cli
 
 
@@ -186,3 +188,56 @@ def test_binary_file_warning(tmpdir):
             "Warning: Skipping file test_dir/binary_file.bin due to UnicodeDecodeError"
             in stderr
         )
+
+
+def test_xml_format_dir(tmpdir):
+    runner = CliRunner()
+    with tmpdir.as_cwd():
+        os.makedirs("test_dir")
+        with open("test_dir/file1.txt", "w") as f:
+            f.write("Contents of file1")
+        with open("test_dir/file2.txt", "w") as f:
+            f.write("Contents of file2")
+
+        result = runner.invoke(cli, ["test_dir", "--cxml"])
+        assert result.exit_code == 0
+        actual = result.output
+        expected = """
+<documents>
+<document path="test_dir/file1.txt">
+Contents of file1
+</document>
+<document path="test_dir/file2.txt">
+Contents of file2
+</document>
+</documents>
+"""
+        assert expected.strip() == actual.strip()
+
+
+def test_cxml_format_multiple_paths(tmpdir):
+    runner = CliRunner()
+    with tmpdir.as_cwd():
+        os.makedirs("test_dir")
+        with open("test_dir/file1.txt", "w") as f:
+            f.write("Contents of file1")
+        with open("test_dir/file2.txt", "w") as f:
+            f.write("Contents of file2")
+
+        result = runner.invoke(
+            cli, ["test_dir/file1.txt", "test_dir/file2.txt", "--cxml"]
+        )
+
+        assert result.exit_code == 0
+        actual = result.output
+        expected = """
+<documents>
+<document path="test_dir/file1.txt">
+Contents of file1
+</document>
+<document path="test_dir/file2.txt">
+Contents of file2
+</document>
+</documents>
+"""
+        assert expected.strip() == actual.strip()