allow git-update-ref create refs with slashes in names

[Alex Riesen <raa.lkml@gmail.com>]

Sorry for the previuos untested patch, the tradition seem to be
catching... This one is actualy tested.

Make git-update-ref create references with slashes in them. git-branch
and git-checkout already support such reference names.

git-branch can use git-update-ref to create the references in a more
formal manner now.

---

the patch also adds to trivial test cases (just to notice regression,
even if I don't believe that is possible for such a trivial thing).

diff --git a/git-branch.sh b/git-branch.sh
index 67f113a..11d52fd 100755
--- a/git-branch.sh
+++ b/git-branch.sh
@@ -102,6 +102,5 @@ rev=$(git-rev-parse --verify "$head") ||
 git-check-ref-format "heads/$branchname" ||
 	die "we do not like '$branchname' as a branch name."
 
-leading=`expr "refs/heads/$branchname" : '\(.*\)/'` &&
-mkdir -p "$GIT_DIR/$leading" &&
-echo $rev > "$GIT_DIR/refs/heads/$branchname"
+git update-ref "refs/heads/$branchname" $rev
+
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 5f98f64..36f7749 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -24,4 +24,12 @@ test_expect_failure \
     'git branch --help should not have created a bogus branch' \
     'test -f .git/refs/heads/--help'
 
+test_expect_success \
+    'git branch abc should create a branch' \
+    'git-branch abc && test -f .git/refs/heads/abc'
+
+test_expect_success \
+    'git branch a/b/c should create a branch' \
+    'git-branch a/b/c && test -f .git/refs/heads/a/b/c'
+
 test_done
diff --git a/update-ref.c b/update-ref.c
index d79dc52..e6fbddb 100644
--- a/update-ref.c
+++ b/update-ref.c
@@ -19,7 +19,8 @@ static int re_verify(const char *path, u
 int main(int argc, char **argv)
 {
 	char *hex;
-	const char *refname, *value, *oldval, *path, *lockpath;
+	const char *refname, *value, *oldval, *path;
+	char *lockpath;
 	unsigned char sha1[20], oldsha1[20], currsha1[20];
 	int fd, written;
 
@@ -49,6 +50,8 @@ int main(int argc, char **argv)
 	}
 	path = strdup(path);
 	lockpath = mkpath("%s.lock", path);
+	if (safe_create_leading_directories(lockpath) < 0)
+		die("Unable to create all of %s", lockpath);
 
 	fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
 	if (fd < 0)