Re: [PATCH v2 12/14] refs: don't store peeled object IDs for invalid tags

> Both the "files" and "reftable" backend store peeled object IDs for
> references that point to tags:
> 
>   - The "files" backend stores the value when packing refs, where each
>     peeled object ID is prefixed with "^".
> 
>   - The "reftable" backend stores the value whenever writing a new
>     reference that points to a tag via a special ref record type.
> 
> Both of these backends use `peel_object()` to find the peeled object ID.
> But as explained in the preceding commit, that function does not detect
> the case where the tag's tagged object and its claimed type mismatch.
> 
> The consequence of storing these bogus peeled object IDs is that we're
> less likely to detect such corruption in other parts of Git.
> git-for-each-ref(1) for example does not notice anymore that the tag is
> broken when using "--format=%(*objectname)" to dereference tags.
> 
> One could claim that this is good, because it still allows us to mostly
> use the tag as intended. But the biggest problem here is that we now
> have different behaviour for such a broken tag depending on whether or
> not we have its peeled value in the refdb.
> 
> Fix the issue by verifying the object type when peeling the object. If
> that verification fails we simply skip storing the peeled value in
> either of the reference formats.
>