GIT_EXTERNAL_DIFF=echo git diff
'
+test_expect_success 'GIT_EXTERNAL_DIFF path counter/total' '
+ write_script external-diff.sh <<-\EOF &&
+ echo $GIT_DIFF_PATH_COUNTER of $GIT_DIFF_PATH_TOTAL >>counter.txt
+ EOF
+ >counter.txt &&
+ cat >expect <<-\EOF &&
+ 1 of 2
+ 2 of 2
+ EOF
+ GIT_EXTERNAL_DIFF=./external-diff.sh git diff &&
+ test_cmp expect counter.txt
+'
+
test_expect_success 'GIT_EXTERNAL_DIFF generates pretty paths' '
touch file.ext &&
git add file.ext &&