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/clan_cli/git.py

@@ -0,0 +1,51 @@
+import subprocess
+from pathlib import Path
+from typing import Optional
+
+from clan_cli.dirs import get_clan_flake_toplevel
+from clan_cli.errors import ClanError
+from clan_cli.nix import nix_shell
+
+
+# generic vcs agnostic commit function
+def commit_file(
+    file_path: Path,
+    repo_dir: Optional[Path] = None,
+    commit_message: Optional[str] = None,
+) -> None:
+    # set default for repo_dir
+    if repo_dir is None:
+        repo_dir = get_clan_flake_toplevel()
+    # check that the file is in the git repository and exists
+    if not Path(file_path).resolve().is_relative_to(repo_dir.resolve()):
+        raise ClanError(f"File {file_path} is not in the git repository {repo_dir}")
+    if not file_path.exists():
+        raise ClanError(f"File {file_path} does not exist")
+    # generate commit message if not provided
+    if commit_message is None:
+        # ensure that mentioned file path is relative to repo
+        commit_message = f"Add {file_path.relative_to(repo_dir)}"
+    # check if the repo is a git repo and commit
+    if (repo_dir / ".git").exists():
+        _commit_file_to_git(repo_dir, file_path, commit_message)
+    else:
+        return
+
+
+def _commit_file_to_git(repo_dir: Path, file_path: Path, commit_message: str) -> None:
+    """Commit a file to a git repository.
+
+    :param repo_dir: The path to the git repository.
+    :param file_path: The path to the file to commit.
+    :param commit_message: The commit message.
+    :raises ClanError: If the file is not in the git repository.
+    """
+    # add the file to the git index
+    subprocess.run(["git", "add", file_path], cwd=repo_dir, check=True)
+    # commit only that file
+    cmd = nix_shell(["git"], ["git", "commit", "-m", commit_message, file_path.name])
+    subprocess.run(
+        cmd,
+        cwd=repo_dir,
+        check=True,
+    )