diff-highlight

#!/bin/sh
##
## Search and use a diff-highlight implementation
## Copyright (c) 2023 SATOH Fumiyasu @ OSSTech Corp., Japan
##
## License: GNU General Public License version 3
##

set -u

if [ -n "${BASH+set}" ]; then
  # shellcheck disable=SC3044 # In POSIX sh, 'shopt' is undefined
  shopt -s lastpipe 2>/dev/null ## Bash 4.2+ for `exec ... |exec ...`
fi

if type perl >/dev/null 2>&1; then
  if [ -n "${GIT_EXEC_PATH+set}" ]; then
    git_prefix="${GIT_EXEC_PATH%/*}/../share"
  else
    git_prefix="/usr/share"
  fi
  git_diff_highlight_dir=$(echo "${git_prefix}"/doc/*git*/contrib/diff-highlight)
  if [ -d "$git_diff_highlight_dir" ]; then
    # shellcheck disable=SC3043 # In POSIX sh, 'local' is undefined
    # shellcheck disable=SC2155 # Declare and assign separately to avoid masking return values
    diff_highlight() {
      local reset="$(tput sgr0)"
      local ul="$(tput smul)"
      local add="$(tput setaf 2)"
      local remove="$(tput setaf 1)"
      local tailspace="$(tput setab 1)"
      exec perl \
	-I"$git_diff_highlight_dir" \
        -MDiffHighlight \
        -e '$SIG{PIPE} = "DEFAULT"; DiffHighlight::highlight_stdin(); exit 0;' \
      |exec sed -E \
        -e "/^diff /,/^\+\+\+ / { s/^/$ul/; s/$/$reset/ }" \
        -e "/^\+.*/ { s/( |　)+$/$tailspace&/; s/^/$add/; s/$/$reset/; }" \
        -e "s/^-.*/$remove&$reset/" \
      ;
    }
  fi
fi

if type diff_highlight >/dev/null 2>&1; then
  diff_highlight
  exit $?
fi

for n in diff-highlight colordiff; do
  for p in /usr/local/bin /usr/bin; do
    c="$p/$n"
    if [ -x "$c" ]; then
      if type nkf >/dev/null 2>&1; then
	exec nkf -x -m0 |exec "$c" "$@"
      else
	exec "$c" "$@"
      fi
      exit $?
    fi
  done
done

exec cat