grep "fatal: invalid ref format: ~a" err
'
+test_expect_success 'branch rejects HEAD as a branch name' '
+ test_must_fail git branch HEAD HEAD^ &&
+ test_must_fail git show-ref refs/heads/HEAD
+'
+
+test_expect_success 'checkout -b rejects HEAD as a branch name' '
+ test_must_fail git checkout -B HEAD HEAD^ &&
+ test_must_fail git show-ref refs/heads/HEAD
+'
+
+test_expect_success 'update-ref can operate on refs/heads/HEAD' '
+ git update-ref refs/heads/HEAD HEAD^ &&
+ git show-ref refs/heads/HEAD &&
+ git update-ref -d refs/heads/HEAD &&
+ test_must_fail git show-ref refs/heads/HEAD
+'
+
+test_expect_success 'branch -d can remove refs/heads/HEAD' '
+ git update-ref refs/heads/HEAD HEAD^ &&
+ git branch -d HEAD &&
+ test_must_fail git show-ref refs/heads/HEAD
+'
+
+test_expect_success 'branch -m can rename refs/heads/HEAD' '
+ git update-ref refs/heads/HEAD HEAD^ &&
+ git branch -m HEAD tail &&
+ test_must_fail git show-ref refs/heads/HEAD &&
+ git show-ref refs/heads/tail
+'
+
+test_expect_success 'branch -d can remove refs/heads/-dash' '
+ git update-ref refs/heads/-dash HEAD^ &&
+ git branch -d -- -dash &&
+ test_must_fail git show-ref refs/heads/-dash
+'
+
+test_expect_success 'branch -m can rename refs/heads/-dash' '
+ git update-ref refs/heads/-dash HEAD^ &&
+ git branch -m -- -dash dash &&
+ test_must_fail git show-ref refs/heads/-dash &&
+ git show-ref refs/heads/dash
+'
+
test_done