Filtering a diff with a regular expression

Question

It seems that it would be extremely handy to be able to filter a diff so that trivial changes are not displayed. I would like to write a regular expression which would be run on the line and then pass it another string that uses the captured arguments to generate a canonical form. If the lines before and after produce the same output, then they would be removed from the diff.

For example, I am working on a PHP code base where a significant number of array accesses are written as my_array[my_key] when they should be my_array["my_key"] to prevent issues if a my_key constant is defined. It would be useful to generate a diff where the only change on the line wasn't adding some quotes.

I can't change them all at once, as we don't have the resources to test the entire code base, so am fixing this whenever I make a change to a function. How can I achieve this? Is there anything else similar to this that I can use to achieve a similar result. For example, a simpler method might be to skip the canonical form and just see if the input is transformed into the output. BTW, I am using Git

Answer 1

grepdiff can be used to filter the hunks in the diff file.

$ git diff -U1 | grepdiff 'console' --output-matching=hunk

It shows only the hunks that match with the given string "console".