Move rewritten blend files instead of copying them

This will cause a nice speedup if the temporary directory happens to be on
the same file system as the target directory for the BAT Pack. This can be
influenced by setting an environment variable; see the documentation for
[tempfile.gettempdir](https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir)

blender_asset_tracer/pack/__init__.py

@@ -265,10 +265,8 @@ class Packer:
         # Copy the asset itself.
         packed_path = action.new_path
         read_path = action.read_from or asset_path
-
-        # TODO(Sybren): if the asset is a rewritten blend file (and thus a copy),
-        # do a move instead of a copy.
-        self._copy_to_target(read_path, packed_path, fc)
+        self._send_to_target(read_path, packed_path, fc,
+                             may_move=action.read_from is not None)
 
         # Copy its sequence dependencies.
         for usage in action.usages:
@@ -284,15 +282,26 @@ class Packer:
             packed_base_dir = first_pp.parent
             for file_path in usage.files():
                 packed_path = packed_base_dir / file_path.name
-                self._copy_to_target(file_path, packed_path, fc)
+                # Assumption: assets in a sequence are never blend files.
+                self._send_to_target(file_path, packed_path, fc)
 
             # Assumption: all data blocks using this asset use it the same way.
             break
 
-    def _copy_to_target(self, asset_path: pathlib.Path, target: pathlib.Path, fc):
+    def _send_to_target(self,
+                        asset_path: pathlib.Path,
+                        target: pathlib.Path,
+                        fc: queued_copy.FileCopier,
+                        may_move=False):
         if self.noop:
             print('%s → %s' % (asset_path, target))
             self._file_count += 1
             return
-        log.debug('Queueing copy of %s', asset_path)
-        fc.queue(asset_path, target)
+
+        verb = 'move' if may_move else 'copy'
+        log.debug('Queueing %s of %s', verb, asset_path)
+
+        if may_move:
+            fc.queue_move(asset_path, target)
+        else:
+            fc.queue_copy(asset_path, target)