Bash multi-line replace t.Error; return -> t.Fatal

replace.sh

#!/usr/bin/env sh
set -eu -o pipefail

git grep -A 1 '\st\.Error' | \
grep 'return$' -B 2 | \
cut -f1 | \
grep -v -- '--' | 
sed 's/.$//' | \
sort | \
uniq | while read filename; do
    echo "$filename"
    cat "$filename" | \
    tr '\n' '\r' | \
    sed -e 's/t.Error\([^\r]\+\)\r[[:blank:]]\+return\r/t.Fatal\1\r/g' | \
    tr '\r' '\n' > t; mv t "$filename"
done