add support for .fengine-reset-ignore

Makefile

@@ -11,3 +11,6 @@ typecheck:
 	poetry run dmypy run -- src tests
 
 pre-commit: fmt lint typecheck
+
+test:
+	poetry run pytest tests

docs/source/tutorials/index.md

@@ -5,4 +5,5 @@
 
 write-template-from-scratch
 backwards-compatible-template-changes
+reset-incarnation
 ```

docs/source/tutorials/reset-incarnation.md

@@ -0,0 +1,14 @@
+# Reset incarnation
+There is an option to reset an incarnation by removing all customizations that were done to it and bring it back to
+a pristine state as if it was just created freshly from the template.
+
+By default, the target version and data is taken from the last change that was successfully applied
+to the incarnation, but they can be overridden. For the data, partial overrides are also allowed.
+
+## Ignore some files from reset
+Sometimes, you want to keep some files in the incarnation that were created or modified after the initial
+creation of the incarnation. For example, you might have a `pipeline.yaml` which is created by different process.
+To achieve this, you can create a file called `.foxops-reset-ignore` in the root of your template. It would propagate it
+to the root of your incarnation repository.
+
+This file should contain a list of file paths (one per line) that should be ignored during the reset process.

src/foxops/services/change.py

@@ -772,11 +772,30 @@ def _construct_merge_request_conflict_description(
     return "\n\n".join(description_paragraphs)
 
 
+def _load_fengine_reset_ignore(directory: Path) -> frozenset[str]:
+    """Load the content of .fengine-reset-ignore file from the given directory.
+    The file contains a list of file/folder names (one per line) that should be
+    skipped during file deletion in delete_all_files_in_local_git_repository.
+    """
+    ignore_file = directory / ".fengine-reset-ignore"
+    if not ignore_file.exists():
+        return frozenset()
+
+    content = ignore_file.read_text()
+    ignore_list = frozenset(line.strip() for line in content.splitlines() if line.strip())
+    return ignore_list
+
+
 def delete_all_files_in_local_git_repository(directory: Path) -> None:
+    ignore_list = _load_fengine_reset_ignore(directory)
+
     for file in directory.glob("*"):
         if file.name == ".git":
             continue
 
+        if file.name in ignore_list:
+            continue
+
         if file.is_dir():
             shutil.rmtree(file)
         else:

tests/services/test_change.py

@@ -714,3 +714,69 @@ async def test_diff_should_not_include_gitrepository(
     diff = await change_service.diff_incarnation(initialized_incarnation.id)
 
     assert diff == ""
+
+
+def test_delete_all_files_in_local_git_repository_respects_fengine_reset_ignore_for_files(tmp_path):
+    # GIVEN
+    (tmp_path / ".fengine-reset-ignore").write_text("keep_me.txt\nkeep_me_too.md")
+    (tmp_path / "keep_me.txt").write_text("I should remain")
+    (tmp_path / "keep_me_too.md").write_text("I should also remain")
+    (tmp_path / "delete_me.txt").write_text("I should be deleted")
+
+    # WHEN
+    delete_all_files_in_local_git_repository(tmp_path)
+
+    # THEN
+    assert (tmp_path / "keep_me.txt").exists()
+    assert (tmp_path / "keep_me_too.md").exists()
+    assert not (tmp_path / "delete_me.txt").exists()
+    assert not (tmp_path / ".fengine-reset-ignore").exists()
+
+
+def test_delete_all_files_in_local_git_repository_respects_fengine_reset_ignore_for_directories(tmp_path):
+    # GIVEN
+    (tmp_path / ".fengine-reset-ignore").write_text("keep_folder")
+    (tmp_path / "keep_folder").mkdir()
+    (tmp_path / "keep_folder" / "nested_file.txt").write_text("Nested content")
+    (tmp_path / "delete_folder").mkdir()
+    (tmp_path / "delete_folder" / "some_file.txt").write_text("To be deleted")
+
+    # WHEN
+    delete_all_files_in_local_git_repository(tmp_path)
+
+    # THEN
+    assert (tmp_path / "keep_folder").exists()
+    assert (tmp_path / "keep_folder" / "nested_file.txt").exists()
+    assert not (tmp_path / "delete_folder").exists()
+
+
+def test_delete_all_files_in_local_git_repository_handles_empty_lines_in_fengine_reset_ignore(tmp_path):
+    # GIVEN
+    (tmp_path / ".fengine-reset-ignore").write_text("keep_me.txt\n\n  \n\nkeep_me_too.md\n")
+    (tmp_path / "keep_me.txt").write_text("I should remain")
+    (tmp_path / "keep_me_too.md").write_text("I should also remain")
+    (tmp_path / "delete_me.txt").write_text("I should be deleted")
+
+    # WHEN
+    delete_all_files_in_local_git_repository(tmp_path)
+
+    # THEN
+    assert (tmp_path / "keep_me.txt").exists()
+    assert (tmp_path / "keep_me_too.md").exists()
+    assert not (tmp_path / "delete_me.txt").exists()
+
+
+def test_delete_all_files_in_local_git_repository_handles_whitespace_in_fengine_reset_ignore(tmp_path):
+    # GIVEN
+    (tmp_path / ".fengine-reset-ignore").write_text("  keep_me.txt  \n  keep_folder  ")
+    (tmp_path / "keep_me.txt").write_text("I should remain")
+    (tmp_path / "keep_folder").mkdir()
+    (tmp_path / "delete_me.txt").write_text("I should be deleted")
+
+    # WHEN
+    delete_all_files_in_local_git_repository(tmp_path)
+
+    # THEN
+    assert (tmp_path / "keep_me.txt").exists()
+    assert (tmp_path / "keep_folder").exists()
+    assert not (tmp_path / "delete_me.txt").exists()