(substitute* "daemon/gdm-session.c"
                  (("^([[:blank:]]*)set_up_session_environment \\(self\\);.*"
                    anchor indent)
                   ;; FIXME: replace hard-coded ~28t with the indent
                   ;; variable. Could use an ugly string-append, or zip the
                   ;; indent in the propagate list... both are inelegant?
                   (format #f "\
~{~28tgdm_session_set_environment_variable (self, ~s, g_getenv (~:*~s));~%~}"
                           propagate))
                  [...]