Re: [PATCH 04/10] get_short_sha1: peel tags when looking for treeish

> The treeish disambiguation function tries to peel tags, but
> it does so by calling:
>
>   deref_tag(lookup_object(sha1), ...);
>
> This will only work if we have previously looked at the tag
> and created a "struct tag" for it. Since parsing revision
> arguments typically happens before anything else, this is
> usually not the case, and we would fail to peel the tag (we
> are lucky that deref_tag() gracefully handles the NULL and
> does not segfault).

> Instead, we can use parse_object(). Note that this is the
> same fix done by 94d75d1 (get_short_sha1(): correctly
> disambiguate type-limited abbreviation, 2013-07-01), but
> that commit fixed only the committish disambiguator, and
> left the bug in the treeish one.

> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  sha1_name.c                         | 2 +-
>  t/t1512-rev-parse-disambiguation.sh | 7 +++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/sha1_name.c b/sha1_name.c
> index 38e51d9..432a308 100644
> --- a/sha1_name.c
> +++ b/sha1_name.c
> @@ -269,7 +269,7 @@ static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_un
>  		return 0;
>  
>  	/* We need to do this the hard way... */
> -	obj = deref_tag(lookup_object(sha1), NULL, 0);
> +	obj = deref_tag(parse_object(sha1), NULL, 0);
>  	if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
>  		return 1;
>  	return 0;
> diff --git a/t/t1512-rev-parse-disambiguation.sh b/t/t1512-rev-parse-disambiguation.sh
> index 30e0b80..dfd3567 100755
> --- a/t/t1512-rev-parse-disambiguation.sh
> +++ b/t/t1512-rev-parse-disambiguation.sh
> @@ -264,6 +264,13 @@ test_expect_success 'ambiguous commit-ish' '
>  	test_must_fail git log 000000000...
>  '
>  
> +# There are three objects with this prefix: a blob, a tree, and a tag. We know
> +# the blob will not pass as a treeish, but the tree and tag should (and thus
> +# cause an error).
> +test_expect_success 'ambiguous tags peel to treeish' '
> +	test_must_fail git rev-parse 0000000000f^{tree}
> +'
> +
>  test_expect_success 'rev-parse --disambiguate' '
>  	# The test creates 16 objects that share the prefix and two
>  	# commits created by commit-tree in earlier tests share a