[git] Add support for subpath to computed destination directory (#15135)

esphome/git.py

@@ -102,6 +102,7 @@ def clone_or_update(
     username: str = None,
     password: str = None,
     submodules: list[str] | None = None,
+    subpath: Path | None = None,
     _recover_broken: bool = True,
 ) -> tuple[Path, Callable[[], None] | None]:
     key = f"{url}@{ref}"
@@ -112,6 +113,9 @@ def clone_or_update(
         )
 
     repo_dir = _compute_destination_path(key, domain)
+    if subpath:
+        repo_dir = repo_dir / subpath
+
     if not repo_dir.is_dir():
         _LOGGER.info("Cloning %s", key)
         _LOGGER.debug("Location: %s", repo_dir)