Implements jeaddons CLI tool

Adds a CLI tool to copy files or folders from a git repository into the current project based on a registry.

The tool provides commands to:
- `add`: Copies files/folders based on registry entries.
- `list`: Lists available registry entries.

Registry entries are defined in `jeAddons/registry.py`.
The tool supports overriding the registry's ref and destination.

jeAddons/copier.py

@@ -4,13 +4,32 @@ import shutil
 from pathlib import Path
 
 
-def fetch_file(repo_url: str, file_path: str, dest: Path):
-    tmp = tempfile.mkdtemp()
+def fetch_path(repo_url: str, repo_path: str, dest: Path, ref: str = "HEAD", force: bool = False):
+    with tempfile.TemporaryDirectory(prefix="jeaddons-") as tmp:
+        tmp_path = Path(tmp)
+        subprocess.check_call(
+            ["git", "clone", "--filter=blob:none", "--no-checkout", "--depth", "1", repo_url, str(tmp_path)]
+        )
+        subprocess.check_call(["git", "-C", str(tmp_path), "sparse-checkout", "init", "--cone"])
+        subprocess.check_call(["git", "-C", str(tmp_path), "sparse-checkout", "set", repo_path])
+        subprocess.check_call(["git", "-C", str(tmp_path), "checkout", ref])
 
-    subprocess.check_call(["git", "clone", "--depth", "1", repo_url, tmp])
+        src = tmp_path / repo_path
+        if not src.exists():
+            raise FileNotFoundError(repo_path)
 
-    src = Path(tmp) / file_path
-    if not src.exists():
-        raise FileNotFoundError(file_path)
+        target = dest / src.name
+        if target.exists():
+            if not force:
+                raise FileExistsError(target)
+            if target.is_dir():
+                shutil.rmtree(target)
+            else:
+                target.unlink()
 
-    shutil.copy2(src, dest / src.name)
+        if src.is_dir():
+            shutil.copytree(src, target)
+            return target
+
+        shutil.copy2(src, target)
+        return target