pkgs/clan/lib: Add clan api to get the relative clan directory

This is a Continuation of: #4519

pkgs/clan-cli/clan_lib/api/directory.py

@@ -170,3 +170,22 @@ def list_system_storage_devices() -> Blockdevices:
     return Blockdevices(
         blockdevices=[blk_from_dict(device) for device in blk_info["blockdevices"]]
     )
+
+
+@API.register
+def get_clan_directory_relative(flake: Flake) -> str:
+    """
+    Get the clan directory path relative to the flake root
+    from the clan.directory configuration setting.
+
+    Args:
+        flake: The clan flake to get the relative directory from
+
+    Returns:
+        The relative directory path (e.g., ".", "direct-config", "subdir/config")
+
+    Raises:
+        ClanError: If the flake evaluation fails or directories cannot be found
+    """
+    _, relative_dir = get_clan_directories(flake)
+    return relative_dir

pkgs/clan-cli/clan_lib/api/directory_test.py

@@ -4,7 +4,7 @@ from pathlib import Path
 import pytest
 from clan_cli.tests.fixtures_flakes import FlakeForTest
 
-from clan_lib.api.directory import get_clan_directories
+from clan_lib.api.directory import get_clan_directories, get_clan_directory_relative
 from clan_lib.errors import ClanError
 from clan_lib.flake import Flake
 
@@ -52,3 +52,42 @@ def test_get_clan_directories_with_direct_directory_config(
     assert "source" in source_dir
 
     assert computed_dir == "direct-config"
+
+
+@pytest.mark.with_core
+def test_get_relative_clan_directory_default(
+    test_flake_with_core: FlakeForTest,
+) -> None:
+    flake = Flake(str(test_flake_with_core.path))
+    relative_dir = get_clan_directory_relative(flake)
+
+    # Default configuration should return "." (which represents current directory)
+    assert relative_dir == "."
+
+
+@pytest.mark.with_core
+def test_get_relative_clan_directory_custom(
+    clan_flake: Callable[..., Flake],
+) -> None:
+    flake = clan_flake(
+        raw="""
+{
+  directory = ./direct-config;
+}
+"""
+    )
+
+    test_subdir = Path(flake.path) / "direct-config"
+    test_subdir.mkdir(exist_ok=True)
+
+    relative_dir = get_clan_directory_relative(flake)
+
+    assert relative_dir == "direct-config"
+
+
+@pytest.mark.with_core
+def test_get_relative_clan_directory_invalid_flake() -> None:
+    invalid_flake = Flake("/non/existent/path")
+
+    with pytest.raises(ClanError):
+        get_clan_directory_relative(invalid_flake)