[PATCH] Fix git-show-branch --current when not on a branch

builtin-show-branch.c relied on resolve_ref() to return
"refs/heads/foo" if on branch foo.  But if not on a branch,
it returns "HEAD".  Hence, `head + pfxlen' (i.e. head+11)
is a memory address beyond the "HEAD" string, so that
further operation leads to access of uninitialized memory.

This commit fixes the bug by just not adding the
"refs/heads/"-length offset.  So append_one_rev() operates
on "refs/heads/foo" instead of "foo", which still works.
But now it also operates correctly on "HEAD".

Signed-off-by: Stephan Beyer <redacted>
---
  builtin-show-branch.c |    3 +--
  1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/builtin-show-branch.c b/builtin-show-branch.c
index 019abd3..412eba0 100644
--- a/builtin-show-branch.c
+++ b/builtin-show-branch.c

@@ -782,8 +782,7 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
  				has_head++;
  		}
  		if (!has_head) {
-			int pfxlen = strlen("refs/heads/");
-			append_one_rev(head + pfxlen);
+			append_one_rev(head);
  		}
  	}

-- 
1.5.5.1