git-fdiff

#!/usr/bin/env bash

# Copyright 2020 Dan Wendorf
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
# documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
# Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

main() {
  local names
  names="$(git diff --name-only "$@")"
  local toplevel
  toplevel="$(git rev-parse --show-toplevel)"

  local flags
  flags="$(git rev-parse --flags "$@")"
  local revs
  revs="$(git rev-parse --revs-only "$@")"

  local preview
  preview="git diff "$flags"  --color=always -- {-1}"

  local path="$(git rev-parse --no-flags --no-revs "$@")"

  local pathlessargs=()
  for arg in "$@"; do
    if [[ "$arg" != "$path" ]]; then
      pathlessargs+=("$arg")
    fi
  done

  pushd "$toplevel" > /dev/null
  < <(echo "$names") fzf -m --ansi --preview "git diff $pathlessargs --color=always -- {-1}" > /dev/null
  popd > /dev/null
}

main "$@"