dotfiles/check_for_update.sh

#!/usr/bin/env zsh
#
# brethil, brutally copied from https://github.com/robbyrussell/oh-my-zsh/blob/master/tools/check_for_upgrade.sh
# This also tries to update amix's vimrc and runs "antigen update"
# 14 July 2017

zmodload zsh/datetime

function _current_epoch() {
  echo $(( $EPOCHSECONDS / 60 / 60 / 24 ))
}

function _update_dotfiles_update() {
  echo "LAST_EPOCH=$(_current_epoch)" >! ~/.dotfiles-update
}

function _upgrade_dotfiles() {
    (cd $DOTFILES; git pull -q --rebase  && echo "Succesfully upgraded dotfiles" || echo "Could not upgrade dotfiles.")
     # amix's vimrc update
     amix_vimrc=$HOME/.vim_runtime
     if [[ -d $amix_vimrc ]]; then
         # the update_plugins.py script makes the vim_runtime dir dirty, so we have to reset --hard
         (cd $amix_vimrc && git reset --hard HEAD >/dev/null && git pull -q --rebase && echo "Upgraded amix's vimrc" || echo "Could not upgrade amix's vimrc" >&2)
         (python $amix_vimrc/update_plugins.py >/dev/null || echo "upgraded amix's vimrc's plugins || "echo "Could not upgrade amix's vimrc's plugins" >&2)
     else
         echo "Could not upgrade amix's vimrc and plugins (missing .vim_runtime folder)" >&2
     fi

    antigen update
    # update the zsh file
    _update_dotfiles_update
}

epoch_target=$UPDATE_ZSH_DAYS
if [[ -z "$epoch_target" ]]; then
     # Default to old behavior
     epoch_target=13
fi

# Cancel upgrade if the current user doesn't have write permissions for the
# dotfiles directory.
[[ -w "$DOTFILES" ]] || return 0

# Cancel upgrade if git is unavailable on the system
whence git >/dev/null || return 0

if mkdir "$DOTFILES/update.lock" 2>/dev/null; then
    if [ -f ~/.dotfiles-update ]; then
      . ~/.dotfiles-update

    if [[ -z "$LAST_EPOCH" ]]; then
      _update_dotfiles_update && return 0;
    fi

    epoch_diff=$(($(_current_epoch) - $LAST_EPOCH))
    if [ $epoch_diff -gt $epoch_target ]; then
      if [ "$DISABLE_UPDATE_PROMPT" = "true" ]; then
        _upgrade_dotfiles
      else
        echo "[brethil dotfiles] Would you like to check for updates? [Y/n]: \c"
        read line
        if [[ "$line" == Y* ]] || [[ "$line" == y* ]] || [ -z "$line" ]; then
          _upgrade_dotfiles
        else
          _update_dotfiles_update
        fi
      fi
    fi
  else
    # create the dotfiles file
    _update_dotfiles_update
  fi

  rmdir $DOTFILES/update.lock
fi