worktree: drop unused code from get_main_worktree()

This code has been unused since fa099d2322 (worktree.c: kill parse_ref()
in favor of refs_resolve_ref_unsafe(), 2017-04-24), so drop it.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

worktree.c

@@ -47,15 +47,12 @@ static void add_head_info(struct worktree *wt)
 static struct worktree *get_main_worktree(void)
 {
 	struct worktree *worktree = NULL;
-	struct strbuf path = STRBUF_INIT;
 	struct strbuf worktree_path = STRBUF_INIT;
 
 	strbuf_add_absolute_path(&worktree_path, get_git_common_dir());
 	if (!strbuf_strip_suffix(&worktree_path, "/.git"))
 		strbuf_strip_suffix(&worktree_path, "/.");
 
-	strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
-
 	worktree = xcalloc(1, sizeof(*worktree));
 	worktree->path = strbuf_detach(&worktree_path, NULL);
 	/*
@@ -69,7 +66,6 @@ static struct worktree *get_main_worktree(void)
 		is_bare_repository();
 	add_head_info(worktree);
 
-	strbuf_release(&path);
 	strbuf_release(&worktree_path);
 	return worktree;
 }