Re: Unexpected cat-file --batch-check output
- From
Jeff King <peff@peff.net>
- Date
- Oct 27, 2021, 01:28 UTC
- Message-ID
- <YXirLGXsKj01uNGv@coredump.intra.peff.net>
- In-Reply-To
- <CAGyf7-Gaphb9q=4cyT0BQa7oYGKXQQsU-XfqvoxfDyijehJO3Q@mail.gmail.com>
On Tue, Oct 26, 2021 at 04:58:49PM -0700, Bryan Turner wrote:
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> > - what does "git rev-parse refs/heads/develop:path/to/parent/file" > > say? If it comes up with 4c8d566ed80, then the problem is cat-file > > specific. If not, then it's a problem in the name resolution > > routines. > > $ /usr/bin/git rev-parse refs/heads/develop > 28a05ce2e3079afcb32e4f1777b42971d7933a91 > $ /usr/bin/git rev-parse refs/heads/develop:path/to/parent/file > cc10f4b278086325aab2f95df97c807c7c6cd75e > > So it looks like rev-parse and cat-file --batch-check both exhibit the > same behavior.
OK, that's not too surprising, since they're using the same routines under the hood. But that does imply that the problem is in the get_oid() family, which is what's doing that name to oid lookup.
I don't recall us ever having a bug of this nature in the history of Git, nor do I think this code would have changed recently. But of course there's a first time for everything.
The parser there isn't exactly left-to-right, so perhaps this particular name is stimulating some corner case. I imagine the answer is "no", or you'd have said so already, but are there any unusual characters in the filename path? Colons, curly braces, etc?
Show 10 quoted lines
> I also had them expand their cat-file --batch-check to include another > file in the same "path/to/parent" directory: > $ echo 'refs/heads/develop > refs/heads/develop:path/to/parent/sibling > refs/heads/develop:path/to/parent/file' | /usr/bin/git cat-file --batch-check > 28a05ce2e3079afcb32e4f1777b42971d7933a91 commit 259 > 2bfe7b4b7c7cdeb9653801d99b65dfefe5780dda blob 897 > cc10f4b278086325aab2f95df97c807c7c6cd75e commit 330 > > So the "sibling" file in the same directory comes out as a "blob", as expected.
Interesting. That again points to their being something funny either with this filename, or perhaps with the tree that contains it.
Show 7 quoted lines
> > - likewise, what does "git cat-file -t cc10f4b27808" say? I'd expect > > it to really be a commit (a bug in batch-check's formatting routines > > could show the wrong object, but I'd expect the oid to at least > > match what ls-tree showed). > > $ /usr/bin/git cat-file -t cc10f4b278086325aab2f95df97c807c7c6cd75e > commit
That's not too surprising. I did wonder if refs/replace or something could be at work here, but I think in that case we'd still report the expected oid. At any rate, we can probably rule that out as rev-parse is returning the same unexpected oid, which means the problem is during the name resolution (and we shouldn't respect refs/replace there at all; we would respect it while reading the outer tree, but then so would your ls-tree, etc).
> I've asked them to double-check whether they can provide me with the > repository, or with an anonymized copy. At this point, it feels like > there's not a lot more I can do/check without access to data that > reproduces the issue so I can attach a debugger.
Another possibility, if they would run a custom Git on their end, is to provide them with a patch that cranks up the debugging output from get_oid_with_context_1(). Though I feel like it's hard to know where to sprinkle printf()s until we know where things go wrong. Is it misinterpreting the name, and not realizing it's a tree:path name? Or is get_tree_entry() at fault? That kind of thing is much easier to figure out interactively in a debugger.
-Peff