abe199808c (git checkout -b: allow switching out of an unborn branch)
introduced a bug demonstrated by
git checkout --orphan foo
git checkout --detach
git symbolic-ref HEAD
which gives 'refs/heads/(null)'.
This happens because we strbuf_addf(&branch_ref, "refs/heads/%s",
opts->new_branch) when opts->new_branch can be NULL for --detach.
Catch and forbid this case, adding a test to t2017 to catch it in
future.
Signed-off-by: Chris Webb <chris@xxxxxxxxxxxx>
---
builtin/checkout.c | 2 ++
t/t2017-checkout-orphan.sh | 6 ++++++
2 files changed, 8 insertions(+)
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e8c1b1f..3980d5d 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -915,6 +915,8 @@ static int switch_unborn_to_new_branch(struct checkout_opts *opts)
int status;
struct strbuf branch_ref = STRBUF_INIT;
+ if (!opts->new_branch)
+ die(_("You are on a branch yet to be born"));
strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
status = create_symref("HEAD", branch_ref.buf, "checkout -b");
strbuf_release(&branch_ref);
diff --git a/t/t2017-checkout-orphan.sh b/t/t2017-checkout-orphan.sh
index 0e3b858..655f278 100755
--- a/t/t2017-checkout-orphan.sh
+++ b/t/t2017-checkout-orphan.sh
@@ -116,4 +116,10 @@ test_expect_success '--orphan refuses to switch if a merge is needed' '
git reset --hard
'
+test_expect_success 'cannot --detach on an unborn branch' '
+ git checkout master &&
+ git checkout --orphan new &&
+ test_must_fail git checkout --detach
+'
+
test_done
--
1.7.10
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