When fsck-ing a loose object, we use object_info's type_name strbuf to
record the parsed object type as a string. For most objects this is
redundant with the object_type enum, but it does let us report the
string when we encounter an object with an unknown type (for which there
is no matching enum value).
There are a few downsides, though:
1. The code to report these cases is not actually robust. Since we did
not pass a strbuf to unpack_loose_header(), we only retrieved types
from headers up to 32 bytes. In longer cases, we'd simply say
"object corrupt or missing".
2. This is the last caller that uses object_info's type_name strbuf
support. It would be nice to refactor it so that we can simplify
that code.
3. Likewise, we'll check the hash of the object using its unknown type
(again, as long as that type is short enough). That depends on the
hash_object_file_literally() code, which we'd eventually like to
get rid of.
So we can simplify things by bailing immediately in read_loose_object()
when we encounter an unknown type. This has a few user-visible effects:
a. Instead of producing a single line of error output like this:
error: 26ed13ce3564fbbb44e35bde42c7da717ea004a6: object is of unknown type 'bogus': .git/objects/26/ed13ce3564fbbb44e35bde42c7da717ea004a6
we'll now issue two lines (the first from read_loose_object() when
we see the unparsable header, and the second from the fsck code,
since we couldn't read the object):
error: unable to parse type from header 'bogus 4' of .git/objects/26/ed13ce3564fbbb44e35bde42c7da717ea004a6
error: 26ed13ce3564fbbb44e35bde42c7da717ea004a6: object corrupt or missing: .git/objects/26/ed13ce3564fbbb44e35bde42c7da717ea004a6
This is a little more verbose, but this sort of error should be
rare (such objects are almost impossible to work with, and cannot
be transferred between repositories as they are not representable
in packfiles). And as a bonus, reporting the broken header in full
could help with debugging other cases (e.g., a header like "blob
xyzzy\0" would fail in parsing the size, but previously we'd not
have showed the offending bytes).
b. An object with an unknown type will be reported as corrupt, without
actually doing a hash check. Again, I think this is unlikely to
matter in practice since such objects are totally unusable.
We'll update one fsck test to match the new error strings. And we can
remove another test that covered the case of an object with an unknown
type _and_ a hash corruption. Since we'll skip the hash check now in
this case, the test is no longer interesting.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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