Shell arguments for `shell-command-to-string` are not enough escaped

[MinoruSekine]

• Shell arguments should be escaped with shell-quote-arguments
  • See https://qiita.com/tadsan/items/17d32514b81f1e8f208a
• Some shell-command-to-string can be replaced with call-process-shell-command, because some of them will not use stdout of shell commands

[MinoruSekine]

215 resolves this.