Merge branch 'js/split-index-fixes'

The index files can become corrupt under certain conditions when the split-index feature is in use, especially together with fsmonitor, which have been corrected. * js/split-index-fixes: unpack-trees: take care to propagate the split-index flag fsmonitor: avoid overriding `cache_changed` bits split-index; stop abusing the `base_oid` to strip the "link" extension split-index & fsmonitor: demonstrate a bug