Problem:
When a broken part is found during the startup, it will clone the parts which are
covered by the broken part, to the detached directory (with the 'covered-by-broken' prefix).
A part may be covered by multiple merged parts, which will result in multiple clones, which
leads to path conflicts and further attempts to clone to the try-n directory. If n exceeds 9,
the clone is abandoned and the table is marked as read-only.
pull#41981 tried fixed the problem, but the fix is incomplete. The metadata_version.txt file
is deleted during covered-by-broken clone. As a result,
looksLikeBrokenDetachedPartHasTheSameContent finds differences during part comparison.
Fix:
covered-by-broken retain metadata_version.txt file when cloning
