fix: perform proper provision in an annex remote

This commit fixes an issue where subdataset provision
did not work if `provision` was invoked from an annex
special remote-process.

The reason for the error was that the special remote
sets the environment variables `GIT_DIR` and
`GIT_WORK_TREE`, which lead to problems in
`datalad.get`.

datalad_remake/commands/provision_cmd.py

@@ -390,7 +390,15 @@ def install_subdataset(
             absolute_path.as_uri(),
         ]
         call_git_lines(args)
-    worktree.get(str(subdataset_path), get_data=False, result_renderer='disabled')
+    stored_environ = dict(os.environ)
+    try:
+        for key in ('GIT_DIR', 'GIT_WORK_TREE'):
+            if key in os.environ:
+                del os.environ[key]
+        worktree.get(str(subdataset_path), get_data=False, result_renderer='disabled')
+    finally:
+        os.environ.clear()
+        os.environ.update(stored_environ)
     uninstalled_subdatasets.remove(subdataset_path)
     uninstalled_subdatasets.update(get_uninstalled_subdatasets(worktree))