Символическая ссылка в виде user@hostname.6912:144780xxxx

bash на помощь.

diff <(sed 's/\(data-refresh-id\)=".*"/\1/;s/\(serverTime\): [0-9]*/\1/' old.txt) \
     <(sed 's/\(data-refresh-id\)=".*"/\1/;s/\(serverTime\): [0-9]*/\1/' new.txt)

Итак, в вашем случае

DIFF_OUTPUT="$(diff <(sed 's/\(data-refresh-id\)=".*"/\1/;s/\(serverTime\): [0-9]*/\1/' old.txt) <(sed 's/\(data-refresh-id\)=".*"/\1/;s/\(serverTime\): [0-9]*/\1/' new.txt))