Percentage value with GNU Diff

Question

What is a good method for using diff to show a percentage difference between two files?

Such as if a file has 100 lines and a copy has 15 lines that have been changed th

Answer 1

https://superuser.com/questions/347560/is-there-a-tool-to-measure-file-difference-percentage has a neat solution for this,

wdiff -s file1.txt file2.txt

more options see man wdiff.