base: Clone git repo if present instead of rsync

I am guessing I may be one of the first people to try using tmt
with a Rust project. The default for the `cargo` toolchain
is to keep a *lot* of cached incremental data in `target/`.
In my case with bootc, it's currently 20G.

A plain rsync() of this is *incredibly* inefficient. rsync doesn't
even use reflinks if available, though that's a distinct bug.

Change the logic here to do a `git clone -s` which is *way*
more efficient; it properly honors my `.gitignore` which
includes `target/`.

Signed-off-by: Colin Walters <[email protected]>

tmt/base.py

@@ -1796,7 +1796,12 @@ def _initialize_worktree(self) -> None:
 
  # Sync metadata root to the worktree
  self.debug(f"Sync the worktree to '{self.worktree}'.", level=2)
- self.run(Command("rsync", "-ar", "--exclude", ".git", f"{tree_root}/", self.worktree))
+ # If we're in a git repository, we just clone it so that we correctly
+ # honor .gitignore, etc.
+ if os.path.isdir(f"{tree_root}/.git"):
+ self.run(Command("git", "clone", "-s", tree_root, self.worktree))
+ else:
+ self.run(Command("rsync", "-ar", "--exclude", ".git", f"{tree_root}/", self.worktree))
 
  def _initialize_data_directory(self) -> None:
  """