clan-cli: add git.commit_file() to auto commit files if inside a git

- commit only if inside a git repo
- commit only the specified file and nothing else
- auto-generate commit message if not specified

pkgs/clan-cli/tests/test_git.py

@@ -0,0 +1,40 @@
+import subprocess
+import tempfile
+from pathlib import Path
+
+import pytest
+
+from clan_cli import git
+from clan_cli.errors import ClanError
+
+
+def test_commit_file(git_repo: Path) -> None:
+    # create a file in the git repo
+    (git_repo / "test.txt").touch()
+    # commit the file
+    git.commit_file((git_repo / "test.txt"), git_repo, "test commit")
+    # check that the repo directory does in fact contain the file
+    assert (git_repo / "test.txt").exists()
+    # check that the working tree is clean
+    assert not subprocess.check_output(["git", "status", "--porcelain"], cwd=git_repo)
+    # check that the latest commit message is correct
+    assert (
+        subprocess.check_output(
+            ["git", "log", "-1", "--pretty=%B"], cwd=git_repo
+        ).decode("utf-8")
+        == "test commit\n\n"
+    )
+
+
+def test_commit_file_outside_git_raises_error(git_repo: Path) -> None:
+    # create a file outside the git (a temporary file)
+    with tempfile.NamedTemporaryFile() as tmp:
+        # commit the file
+        with pytest.raises(ClanError):
+            git.commit_file(Path(tmp.name), git_repo, "test commit")
+
+
+def test_commit_file_not_existing_raises_error(git_repo: Path) -> None:
+    # commit a file that does not exist
+    with pytest.raises(ClanError):
+        git.commit_file(Path("test.txt"), git_repo, "test commit")