`pull --rebase --autostash` fails when fast forward in dirty repo

[Tyler Brazier <tylerbrazier@gmail.com>]

Hi,

This script explains and tests what's going on:
https://gist.github.com/tylerbrazier/4478e76fe44bf6657d4d3da6c789531d

pull is failing because it shortcuts to --ff-only then calls
run_merge(), which does not know how to autostash. Removing the
shortcut fixes the problem:

diff --git a/builtin/pull.c b/builtin/pull.c
index dd1a4a94e..225a59f5f 100644
--- a/builtin/pull.c
+++ b/builtin/pull.c
@@ -868,11 +868,6 @@ int cmd_pull(int argc, const char **argv, const
char *prefix)
      head = lookup_commit_reference(orig_head.hash);
      commit_list_insert(head, &list);
      merge_head = lookup_commit_reference(merge_heads.oid[0].hash);
-     if (is_descendant_of(merge_head, list)) {
-         /* we can fast-forward this without invoking rebase */
-         opt_ff = "--ff-only";
-         return run_merge();
-     }
      return run_rebase(&curr_head, merge_heads.oid, &rebase_fork_point);
  } else {
      return run_merge();