From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 19 Jun 2013 18:38:38 GMT
Subject: Re: [PATCH] peel_onion(): add support for <rev>^{tag}
Message-ID: <7vvc5aymhd.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1371605946-32565-1-git-send-email-rhansen@bbn.com>

Richard Hansen <rhansen@bbn.com> writes:

> gitrevisions(7) implies that <rev>^{tag} should work,...

Does it?  Is it possible that that should be fixed?

What does it even _mean_ to peel something to a TAG?

A commit, a tree or a blob cannot be peeled to a tag---none of them
can contain a tag.

When you have a tag that points at something else, what you have is
already a tag, so <that-tag>^{tag} would be <that-tag> itself.

Even more confusingly, when you have a tag that points at another
tag, what does <that-outer-tag>^{tag} mean?  The outer tag itself,
or do you need to peel at least once to reveal the inner-tag?  What
if that inner-tag points at yet another tag?

The patch does not touch peel_to_type(), so your answer to the above
question seems to be "if T is already a tag, T^{tag} is T itself",
but then that operation does not look all that useful.

Confused...

> diff --git a/sha1_name.c b/sha1_name.c
> index 90419ef..68fd0e4 100644
> --- a/sha1_name.c
> +++ b/sha1_name.c
> @@ -677,6 +677,8 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
>  	sp++; /* beginning of type name, or closing brace for empty */
>  	if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
>  		expected_type = OBJ_COMMIT;
> +	else if (!strncmp(tag_type, sp, 3) && sp[3] == '}')
> +		expected_type = OBJ_TAG;
>  	else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
>  		expected_type = OBJ_TREE;
>  	else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')