Auto back up of any files to Github

cron_git_arbitray_file.sh

#!/bin/bash

# Back up specific files on any directories.
# Using cron job, check update for each file.
# Up-to-date files are copied to local repository
# and pushed to github.
#
# Usage: 
#   $ bash ./cron_git_arbitray_file.sh
# cron example. execute at every 4am: 
#   0 4 * * * (cd /home/dir/of/sh/ && bash cron_git_arbitrary_file.sh)
# Log: ./log/yyyymmdd.log is saved.

#
# Parameters
# ----------
# declare -a List=(
#   "/home/user/full/path/to/file.file"
#   "/home/user/.config/path/to/file.file"
# )
# REMOTE_REPO="github.com/username/reponame.git"
# LOCAL_REPO="/home/user/local/reponame/"
# SUBDIR_REPO="sub-dir-in-repo/" # optional
# USERNAME="github-username"
# PASSWORD="password-token"
# ----------

# Set files to auto backup
declare -a List=(
  "/home/user/full/path/to/file.file"
  "/home/user/.config/path/to/file.file"
)

source ./.env
REMOTE_REPO="github.com/username/reponame.git"
LOCAL_REPO="/home/user/local/reponame/"
SUBDIR_REPO="sub-dir-in-repo/" # optional
USERNAME="github-username"
PASSWORD=$MY_TOKEN

# <dir_of_sh>/log/YYYYMMDD.log is created.
PWD=$(pwd)
log_file=$PWD"/log/$(date +%Y%m%d).log"
mkdir -p $PWD"/log" && touch $log_file

# confirm SUBDIR_REPO exists
mkdir -p $LOCAL_REPO$SUBDIR_REPO

# main
echo "----- $(date +%Y/%m/%d-%H:%M:%S): $(basename "$0") -----" >>$log_file
cd $LOCAL_REPO
update_cnt=0

# check update for each item
for item in "${List[@]}"; do

  # full/path/file to full_path_file
  filename_full=$SUBDIR_REPO"${item//\//_}"

  file1=$item
  file2=$LOCAL_REPO$filename_full
  echo "Update check: "$file1 >>$log_file

  command1="date +%Y%m%d%H%M%S -r "$file1
  command2="date +%Y%m%d%H%M%S -r "$file2

  a=$(eval $command1)
  b=$(eval $command2)

  if [[ $a -eq $b ]]; then

    echo "  No update." >>$log_file

  else

    echo "  Found update. Copy it to local repo. Git add, commit, push." >>$log_file

    ((update_cnt = update_cnt + 1))

    cp -p $file1 $file2

    $(eval "git add "$file2)

  fi
done

if [[ $update_cnt -gt 0 ]]; then
  git commit -m "Automatic back up"
  git push -u https://$USERNAME:$PASSWORD@$REMOTE_REPO master >/dev/null 2>&1
fi