On 2013-06-19 14:38, Junio C Hamano wrote:
> Richard Hansen <rhan...@bbn.com> writes:
>
>> gitrevisions(7) implies that <rev>^{tag} should work,...
>
> Does it? Is it possible that that should be fixed?
Depends on whether you think ^{tag} is a useful feature or not; see below.
>
> What does it even _mean_ to peel something to a TAG?
It's the same as peeling something to any other object type: If the
object is that type, done. Otherwise dereference and try again. If it
can't be dereferenced, barf.
>
> A commit, a tree or a blob cannot be peeled to a tag---none of them
> can contain a tag.
Right, so all of those would barf.
>
> 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.
Exactly, just like <object>^{object} is <object> 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.
Barfing on non-tags is the feature this adds. It's otherwise useless,
just like <object>^{object} is useless except to barf when <object>
doesn't exist.
It's a sometimes-convenient way to assert that an object specifier
refers to a tag object and not something else. For example, instead of:
fatal() { printf %s\\n "ERROR: $*" >&2; exit 1; }
type=$(git cat-file -t "$1") || fatal "$1 is not a valid object"
[ "${type}" = tag ] || fatal "$1 is not a tag object"
use "$1" here
you can do:
use "$1"^{tag} here
-Richard
>
> 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] == '}')
>
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