desktop-file-name-format

desktop-file-name-format is a variable defined in `desktop.el'.
Its value is

absolute

Documentation:
Format in which desktop file names should be saved.
Possible values are:
absolute -- Absolute file name.
tilde -- Relative to ~.
local -- Relative to directory of desktop file.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.