BSD xargs does not have the -d option. Here we use tr to convert
newlines to NUL characters, then pass -0 to xargs (which BSD does
support).
I looked at passing -z to 'git ls-files', but I did not find a BSD
grep option to turn on NUL deliminted line processing.
# based on the FSF guideline, for want of a better idea.
THRESHOLD=15
-git ls-files | grep -v -e "$FILE_EXCLUDE" | xargs -n 1 -d \\n \
+git ls-files | grep -v -e "$FILE_EXCLUDE" | tr '\n' '\0' | xargs -0 -n 1 \
git blame -w --line-porcelain -- | \
sed -n "/$AUTHOR_EXCLUDE/d; s/^[aA][uU][tT][hH][Oo][rR] //p" | \
sort -fd | uniq -ic | awk "\$1 >= $THRESHOLD" | sort -nr