git: 'update-cached-checkout' returns the commit ID when given a tag.

Previously, starting with commit
efa578ecaece67366b4b0e2266de7c2faaa4ae54, 'update-cached-checkout' would
return the OID of the annotated tag the tag points to.  With this change
it returns the OID of the commit object in all cases.

* guix/git.scm (resolve-reference): In the 'tag' case, call
'tag-target-id' and 'tag-lookup' when OID designates an annotated tag.
* tests/git.scm ("update-cached-checkout, tag"): New test.

1 files changed, 9 insertions, 6 deletions

diff --git a/guix/git.scm b/guix/git.scm
index 10e6dcaf23..95630a5e69 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -272,12 +272,15 @@ corresponding Git object."
                   ;; There's no such tag, so it must be a commit ID.
                   (resolve `(commit . ,str)))))))
       (('tag    . tag)
-       (let ((oid (reference-name->oid repository
-                                       (string-append "refs/tags/" tag))))
-         ;; OID may point to a "tag" object, but it can also point directly
-         ;; to a "commit" object, as surprising as it may seem.  Return that
-         ;; object, whatever that is.
-         (object-lookup repository oid))))))
+       (let* ((oid (reference-name->oid repository
+                                        (string-append "refs/tags/" tag)))
+              (obj (object-lookup repository oid)))
+         ;; OID may designate an "annotated tag" object or a "commit" object.
+         ;; Return the commit object in both cases.
+         (if (= OBJ-TAG (object-type obj))
+             (object-lookup repository
+                            (tag-target-id (tag-lookup repository oid)))
+             obj))))))
 
 (define (switch-to-ref repository ref)
   "Switch to REPOSITORY's branch, commit or tag specified by REF.  Return the