tracking branch on a tag

Hi

So i set up a tracking branch on an annotated signed tag like:


$git branch --track foobranch v2.6.26
 >Branch foobranch set up to track local ref refs/tags/v2.6.26.

Check it out, get an error

$git checkout foobranch
 >Switched to branch 'foobranch'
 >error: Object 14650d6ec137e70b6c1918cdef235027c5156020 is a commit, 
not a tag
 >fatal: Invalid symmetric difference expression 
bce7f793daec3e65ec5c5705d2457b81fe7b5725...14650d6ec137e70b6c1918cdef235027c5156020

Inspect the relevant object

$git-cat-file -p bce7f793daec3e65ec5c5705d2457b81fe7b5725
 >tree 05bc81f9b27a1ab60ea4e506357f0c7f2ece4eda
 >parent ec229e830060091b9be63c8f873c1b2407a82821
 >author Linus Torvalds [off-list ref] 1215985889 -0700
 >committer Linus Torvalds [off-list ref] 1215985889 -0700

 >Linux 2.6.26

$git-cat-file -p 14650d6ec137e70b6c1918cdef235027c5156020
 >object bce7f793daec3e65ec5c5705d2457b81fe7b5725
 >type commit
 >tag v2.6.26
 >tagger Linus Torvalds [off-list ref] Sun Jul 13 
 >14:51:38 2008 -0700
 >
 >Linux 2.6.26
 >-----BEGIN PGP SIGNATURE-----
 >Version: GnuPG v1.4.9 (GNU/Linux)
 >
 >iEYEABECAAYFAkh6ePIACgkQF3YsRnbiHLuJcACgpHzd21qAY25V2VQWBCYPW8bB
 >Z8MAoJ9qfiwuRt27cdrmAU2aJq+YFrYs
 >=aHK8
 >-----END PGP SIGNATURE-----

I get this errors only on annotated/signed tags, not on lightweight 
tags. Admittedly it doesnt make much sense to track a tag, yet this 
error message makes even less sense:

error: Object 14650d6ec137e70b6c1918cdef235027c5156020 is a commit, not 
a tag

with 14650d being a tag.

Is this error message serious, as fatal sound quite harsh? Can it be 
avoided, by guiding the user on  branch creation or by simply not 
showing it in this situation?

Gruessle
Simon

stat_tracking_info() assumes that upstream references (as specified by
--track or set up automatically) are commits. By calling lookup_commit()
on them, create_objects() creates objects for them with type commit no
matter what their real type is; this disturbs lookup_tag() later on the
call sequence, leading to git status, git branch -v  and git checkout
erroring out.

Fix this by using lookup_commit_reference() instead so that (annotated)
tags can be used as upstream references.

Signed-off-by: Michael J Gruber <redacted>
---
I'm sorry I won't be able to write a test any more today. Please let me
whether it's okay without a test.

 remote.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/remote.c b/remote.c
index d66e2f3..2c3e905 100644
--- a/remote.c
+++ b/remote.c

@@ -1399,13 +1399,13 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	base = branch->merge[0]->dst;
 	if (!resolve_ref(base, sha1, 1, NULL))
 		return 0;
-	theirs = lookup_commit(sha1);
+	theirs = lookup_commit_reference(sha1);
 	if (!theirs)
 		return 0;
 
 	if (!resolve_ref(branch->refname, sha1, 1, NULL))
 		return 0;
-	ours = lookup_commit(sha1);
+	ours = lookup_commit_reference(sha1);
 	if (!ours)
 		return 0;
 

-- 
1.6.3.rc3