Subject: Re: [RFC PATCH] fast-export, fast-import: Let tags specify an internal name

From: Luke Shumaker <[email-masked]>
Date: Wed, 21 Apr 2021 11:26:17 -0600

On Wed, 21 Apr 2021 10:34:28 -0600,
Luke Shumaker wrote:
> On Wed, 21 Apr 2021 02:03:57 -0600,
> Ævar Arnfjörð Bjarmason wrote:
> > On Tue, Apr 20 2021, Luke Shumaker wrote:
> > > +	tagname = memmem(buf, message ? message - buf : size, "\ntag ", 5);
> > > +	if (!tagname)
> > > +		die("malformed tag %s", oid_to_hex(&tag->object.oid));
> > > +	tagname += 5;
> > > +	tagname_end = strchrnul(tagname, '\n');
> > 
> > So it's no longer possible to export a reporitory with a missing "tag"
> > entry in a tag? Maybe OK, but we have an escape hatch for it with fsck,
> > we don't need one here?
> > 
> > In any case a test for it would be good to have.
> 
> I hadn't realized that it was possible for a tag object to be missing
> the "tag" entry, I will fix that.

Actually, can you expand on that?  I don't see the escape hatch you
speak of.

`git hash-object` doesn't want to even create such an object ("fatal:
corrupt tag"), and I had to pass `--literally` to even create the
object.

`git update-ref` doesn't want to even acknowledge the object to create
the ref pointing to it ("fatal: cannot update ref 'refs/tags/badtag':
trying to write ref 'refs/tags/badtag' with nonexistent object HASH"),
and I had to `echo HASH > .git/refs/tags/badtag` to create the ref.

And then `git fsck` (even with `--no-tags`) complains about the object
("error: HASH: object could not be parsed: .git/objects/HA/SH").

It is my reading of the code that `parse_tag_buffer` will always fail
to parse such an object, and so `fsck_walk_tag` and `fsck_walk` will
always bubble up an error.

-- 
Happy hacking,
~ Luke Shumaker