In commit 6bb35878 ("clone: set refs/remotes/origin/HEAD to default
branch when branch is specified, attempt 2") libgit2 was changed to set
the default remote branch when one was copied.

But it makes update_head_to_branch() return an error if the origin
doesn't even *have* a HEAD in the first place, since
git_remote_default_branch() will fail.

That's entirely wrong, and means that you cannot do "git_clone()" of a
particular branch on a remote repository when that remote doesn't have a
default branch at all.

So don't set the error code.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>