Convert "svn status" absolute paths to relative immediately

Solves problem, introduced in 23f70a993dfc35267b149d6b12fe4398170f0d48, where absolute paths have made their way to final diff, that was submitted to Differential.
Merge branch 'T6437-svn-changelist-support'

* T6437-svn-changelist-support:
  Convert "svn status" absolute paths to relative immediately