Add prefix to the src/href output path

I have a use case where I use gulp to build a Wordpress theme. The src/href output path created by useref is relative to the directory containing the theme, but the website runs relative to the root directory. So if I use

```

```

the website looks for the 'combined.css' file in 'mydomain.com/css/combined.css', when in reality its location is something like this: 'mydomain.com/wp-content/themes/sometheme/css/combined.css'.

Wordpress has a php function to generate a path to the root of the theme like this: ``. Right now I just add this manually to the places where I have useref blocks, but it would be much easier if I could just have useref prefix this using the options, since now I have to remember to add the above line every time i deploy my theme.

I tried just adding the Wordpress code in the blocks like this:

```

```

This would make the path inserted in the href attribute look correct, but gulp-useref would fail (it basically doesn't stop running at all - never halts the process). I guess the reason is obvious - useref now tries to create the 'combined.css' in a directory called '/css/' (which I assume is illegal).

Is there any way to prefix or add a base path to the src/href output path, without changing the actual path the 'combined.css' file is stored at?