After upgrading a recent Hudson installation to 1.352, I'm unable to use an alternate settings.xml file. See the log:

—
<===[HUDSON REMOTING CAPACITY]===>channel started
Executing Maven: -B -f c:\hudson-slave\workspace\my-job-name\pom.xml -s ../wde/config/maven/settings.xml clean install -X

WARNING: Alternate user settings file: ../wde/config/maven/settings.xml is invalid. Using default path.
—

Please note that I want to use the file that exists at:

c:\wde\config\maven\settings.xml

So, I have configured the field 'Alternate settings file' to have this value:
../../../wde/config/maven/settings.xml

The help text says that 'This path is relative to the workspace root.'

I guess the workspace root in my case is:
c:\hudson-slave\workspace\my-job-name\

So, '../../../' would strip 3 directories, leading us to just 'c:'

The issue also exists on version 1.351