bash script to automatically download and update vim plugins (lightweight alternative to a plugin manager using native vim 8 packages)

vim-update-plugins.sh

#!/bin/bash

# == USAGE ==
# Put Github URLs inside a file called `plugins.start.txt` inside your vim
# directory (either `$HOME/.vim/plugins.start.txt` or
# `$HOME/.config/nvim/plugins.start.txt`). Then, run this script which will
# clone or update the plugins accordingly.
#
# == EXAMPLE ==
# $ cat "$HOME/.config/nvim/plugins.start.txt"
# https://github.com/tpope/vim-commentary
# https://github.com/tpope/vim-eunuch
# https://github.com/andymass/vim-matchup
# https://github.com/romainl/vim-qlist
# https://github.com/tpope/vim-repeat
# https://github.com/mhinz/vim-signify
# https://github.com/tpope/vim-sleuth
# https://github.com/tpope/vim-surround
# https://github.com/moll/vim-bbye
# https://github.com/nvim-lua/plenary.nvim
# https://github.com/nvim-telescope/telescope.nvim
# https://github.com/lambdalisue/fern.vim
# https://github.com/neovim/nvim-lspconfig
# https://github.com/tpope/vim-unimpaired
#
# == NOTES ==
# 1) To update optional plugins, put the URLs in `plugins.opt.txt` instead.
# 2) Empty lines or lines starting with '#' are ignored (useful for comments).
# 3) You can change the pack/* name by changing the first part of the filename
# e.g. plugins in `foo.start.txt` will be downloaded to `pack/foo/start/`,
# plugins in `foo.opt.txt` will be downloaded to `pack/foo/opt/`.

# update_plugins takes in a directory path and updates a bunch of plugins in it
# according to vim 8 native package loading rules.
update_plugins() {
  # update_plugin takes in a URL and git clones or git pulls it in the current
  # directory.
  update_plugin() {
    URL="$(echo "$1" | xargs)" # trim space
    case $URL in
      '#'*) return ;; # ignore comments
      '')   return ;; # ignore empty lines
    esac
    dir="$(basename "$URL")"
    if [ ! -d "$dir" ]; then
      git clone --depth 1 "$1"
      return $?
    fi
    if ! pushd "$dir"; then
      return $? # failed to enter $dir
    fi
    if ! git pull --depth 1 --ff-only; then
      # git pull --ff-only failed, fallback to forcibly overwriting local copy
      git fetch --all --depth 1 && git reset --hard "origin/$(git branch | grep '*' | cut -d' ' -f2)"
    fi
    popd 2>/dev/null 1>&2
  }
  export -f update_plugin

  ROOT_DIR="$1" # $ROOT_DIR is either $HOME/.vim or $HOME/.config/nvim
  if [ ! -d "$ROOT_DIR" ]; then
    return
  fi
  for filepath in $(find "$ROOT_DIR" -type f -name '*.start.txt' -o -name '*.opt.txt'); do
    # e.g.
    # filepath: $HOME/.vim/plugins.start.txt
    # filename: plugins.start
    # dirname : plugins
    # dirtype : start
    # dir     : $HOME/.vim/pack/plugins/start
    filename="$(basename "${filepath%.txt}")"
    dirname="${filename%.*}"
    if [ ! "$dirname" ]; then
      continue
    fi
    dirtype="${filename##*.}"
    dir="$ROOT_DIR/pack/$dirname/$dirtype"
    mkdir -p "$dir"
    pushd "$dir"
    # update each plugin in parallel with xargs
    cat "$filepath" | xargs -I{} -P10 sh -c 'update_plugin {}'
    popd 2>/dev/null 1>&2
  done
  case $ROOT_DIR in
    *nvim*) command -v nvim >/dev/null 1>&2 && nvim --headless -c 'helptags ALL' -c 'q!' >/dev/null 1>&2 ;;
    *.vim*) command -v vim >/dev/null 1>&2 && vim -c 'helptags ALL' -c 'q!' >/dev/null 1>&2 ;;
  esac
}

VIM_ROOT="$HOME/.vim"
NVIM_ROOT="${XDG_CONFIG_HOME:-$HOME/.config}/nvim"
SCRIPT_NAME="$(basename "${BASH_SOURCE[0]}")"
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]:-$PWD}")" 2>/dev/null 1>&2 && pwd)"
has_prefix() { case $1 in "$2"*) true;; *) false;; esac }

if   has_prefix "$PWD" "$VIM_ROOT";         then update_plugins "$VIM_ROOT"  # are we in $VIM_ROOT?
elif has_prefix "$PWD" "$NVIM_ROOT";        then update_plugins "$NVIM_ROOT" # are we in $NVIM_ROOT?
elif has_prefix "$SCRIPT_DIR" "$VIM_ROOT";  then update_plugins "$VIM_ROOT"  # is script in $VIM_ROOT?
elif has_prefix "$SCRIPT_DIR" "$NVIM_ROOT"; then update_plugins "$NVIM_ROOT" # is script is $NVIM_ROOT?
else
  update_plugins "$VIM_ROOT"
  update_plugins "$NVIM_ROOT"
fi