git pre-push script to mirror pushed files to another directory

pre-push

#!/bin/bash
# git pre-push script to mirror pushed files to another directory
destdir=/mirror-dir
if [ `git branch --show-current` != "main" ]; then
    echo "pre-push: Not on main branch - skipping"
else
    echo "pre-push: Mirroring to $destdir"
    (git diff @{push} @ --diff-filter=ACMR --name-only | while read file; do
        echo "pre-push: Copying $file"
    install -D "$file" "$destdir/$file"
        retVal=$?
        if [ $retVal -ne 0 ]; then
            echo "pre-push: Error " $retVal
            exit $retVal
        fi
    done) || exit
    (git diff @{push} @ --diff-filter=D --name-only | while read file; do
        echo "pre-push: Deleting $file"
        rm "$destdir/$file"
        retVal=$?
        if [ $retVal -ne 0 ]; then
            echo "pre-push: Error " $retVal
            exit $retVal
        fi
    done) || exit
    echo "pre-push: OK"
fi
exit 0