* pygit2: disable set_ref with reflog message
* git: implement is_dirty in dulwich
* pygit2: implement _stash_apply
* pygit: update to 1.5.0
* enable set_ref(message=...) for pygit2
* git: replace backend reflog_delete in favor of _stash_drop
* pygit: support stash_push with custom refs
* update tests for backend stash_drop behavior
* pygit: raise MergeConflictError on failed stash apply
* pygit: reload index from disk before stash apply
* update stash_apply checkout strategy
* mark flaky test