A git pre-commit hook to reject changes which would result in non clang-formatted files

clangformat-precommit-hook

#!/bin/sh
#
# This pre-commit hook checks if any versions of clang-format
# are installed, and if so, uses the installed version to reject
# un-clang-formatted commits

maj_min=1
maj_max=3

base=clang-format
format=""

# Redirect output to stderr.
exec 1>&2

 # check if clang-format is installed
type "$base" >/dev/null 2>&1 && format="$base"

# if not, check all possible versions
# (i.e. clang-format-<$maj_min-$maj_max>-<0-9>)
if [ -z "$format" ]
then
    for j in `seq $maj_max -1 $maj_min`
    do
        for i in `seq 0 9`
        do
            type "$base-$j.$i" >/dev/null 2>&1 && format="$base-$j.$i" && break
        done
        [ -z "$format" ] || break
    done
fi

# no versions of clang-format are installed
if [ -z "$format" ]
then
    echo "$base is not installed. Pre-commit hook will not be executed."
    exit 0
fi

git diff --cached --name-only --diff-filter=ACMRT | grep -E "\.h$|\.cpp$|\.tcc$|\.tpp$|\.hpp$" | xargs -n1 clang-format -style=file -output-replacements-xml | grep "<replacement " >/dev/null
if [ $? -ne 1 ]
then 
    echo "Commit did not match clang-format"
    exit 1;
fi