show-branch: avoid segfault with --reflog of unborn branch

When no branch is given to the "--reflog" option, we resolve
HEAD to get the default branch. However, if HEAD points to
an unborn branch, resolve_ref returns NULL, and we later
segfault trying to access it.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index 408ce7030731f765228de93066a815bd4db59e30..092b59b0b3c0782a9802b9c3200d5523ac4e2e3e 100644 (file)
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -743,6 +743,8 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
                        fake_av[1] = NULL;
                        av = fake_av;
                        ac = 1;
+                       if (!*av)
+                               die("no branches given, and HEAD is not valid");
                }
                if (ac != 1)
                        die("--reflog option needs one branch name");