Shell script to copy a file in a git repository while retaining its history

git-cp.sh

#!/bin/sh
#
# Duplicates a file in git, retaining history for the copy
# This requires four commits that cannot(?) be squased
# Inspired by https://stackoverflow.com/q/3887736
# Deprecated by https://github.com/tj/git-extras/blob/main/bin/git-cp

if [ "$#" -ne 2 ]
then
  echo "Usage: $(basename "$0") source destination"
  exit 1
fi

MESSAGE="Copy \"$1\" to \"$2\" with history"

# Rename and commit the destination file
git mv "$1" "$2"
git commit -n -m "${MESSAGE} (create new file)"

# Go back, rename and commit a temp copy
REV=$(git rev-parse HEAD)
git reset --hard HEAD^
# TODO(sparr): Handle foo.temp already existing
git mv "$1" "$1.temp"
git commit -n -m "${MESSAGE} (create temp file)"

# Merge the two two commits above, leaving two files
git merge "${REV}"
git commit -a -n -m "${MESSAGE} (merge)"

# Rename the temp file back to the original source file
git mv "$1.temp" "$1"
git commit -n -m "${MESSAGE} (rename temp file)"