How do I use git clean/smudge to update a placeholder value in a text file to an absolute path?

Question

I have an eclipse .classpath file committed to a git repository. The file is shared between Windows and Linux systems. On Windows, some entries require an absolute path for Eclipse to detect that the referred-to paths exist on the filesystem. For example:

<classpath>
    <!-- this relative path works fine (jar file) -->
    <classpathentry kind="lib" path="../../otherApp/lib/opencsv-2.3.jar"/>

    <!-- this relative path makes Eclipse complain ('conf' is a directory) -->
    <classpathentry kind="lib" path="../../otherApp/conf"/>

    <!-- However, using the absolute path works -->
    <classpathentry kind="lib" path="D:/sandbox/otherApp/conf"/>
</classpath>

When referring to a directory using a relative path, eclipse gives the following error:

Project 'myApp' is missing required library: 'D:\sandbox\otherApp\conf'

The directory is present, and when a full path is provided, this works just fine.

To solve, I considered putting a placeholder in the .classpath file committed to our git repository, and using a git "content filter" with smudge and clean scripts to change the placeholder to the appropriate absolute path on each developer's machine. How might I accomplish this?