builtin-checkout.c: Remove unused prefix arguments in switch_branches path

This path doesn't actually care where in the tree you started out,
since it must change the whole thing anyway. With the gratuitous bug
removed, the argument is unused.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-checkout.c

@@ -205,8 +205,7 @@ static void setup_branch_path(struct branch_info *branch)
 }
 
 static int merge_working_tree(struct checkout_opts *opts,
-			      struct branch_info *old, struct branch_info *new,
+			      struct branch_info *old, struct branch_info *new)
-			      const char *prefix)
 {
 	int ret;
 	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
@@ -429,8 +428,7 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 		adjust_to_tracking(new, opts);
 }
 
-static int switch_branches(struct checkout_opts *opts,
+static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
-			   struct branch_info *new, const char *prefix)
 {
 	int ret = 0;
 	struct branch_info old;
@@ -471,7 +469,7 @@ static int switch_branches(struct checkout_opts *opts,
 		opts->force = 1;
 	}
 
-	ret = merge_working_tree(opts, &old, new, prefix);
+	ret = merge_working_tree(opts, &old, new);
 	if (ret)
 		return ret;
 
@@ -569,5 +567,5 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		die("Cannot switch branch to a non-commit.");
 	}
 
-	return switch_branches(&opts, &new, prefix);
+	return switch_branches(&opts, &new);
 }