How to grep the git diff?

Question

Is there a way to show the git-diff filtered by a given pattern.

Something like

git grepdiff pattern

changed file
+++ some sentence with pattern
change         


        

Answer 1

Here is a custom diff tool that allows grepping inside changes (but not the context):

Usage

GIT_EXTERNAL_DIFF="mydiff --grep foo" git diff

This will output those lines in your changes that contain foo (including lines where foo disappeared because of your changes). Any grep pattern can be used instead of foo.

Each output line starts with the following prefix:

filename: oldlinenum: newlinenum|

The script can also be used without the --grep option, in which case it simply formats the full diff (i.e. providing full context) as described above.

mydiff

#!/bin/bash

my_diff()
{
    diff --old-line-format="$1"':%6dn:      |-%L'     \
         --new-line-format="$1"':      :%6dn|+%L'     \
         --unchanged-line-format="$1"':%6dn:%6dn| %L' \
         $2 $3
}

if [[ $1 == '--grep' ]]
then
    pattern="$2"
    shift 2
    my_diff "$1" "$2" "$5"|grep --color=never '^[^|]\+|[-+].\+'"$pattern"'.*'
else
    my_diff "$1" "$2" "$5"
fi

exit 0