Fix no-fetch behavior

[ikesyo]

Ref: #18

An option with no- prefix returns false.

https://docs.ruby-lang.org/ja/latest/class/OptionParser.html

また、"no-" をオプションの先頭に付けた場合は値が反転します。

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Currently @no_fetch is either nil or false, so git :remote, 'update', 'origin' unless @no_fetch will be executed always.

[ikesyo]

Hmm we still need to be able to access remote repos when running git('ls-remote', 'origin', 'refs/pull/*/head') 😞

So I assume that --no-fetch option is insufficient or useless.

[Songmu]

Indeed, as @ikesyo wrote, this change does not fulfill the original purpose. However, it's terrible that --no-fetch is currently not fully working, and in the meantime, implementing this option will reduce execution time, albeit by a few tenths of a second.

So I think there are two choices.

• Merge this change
• eliminate the --no-fetch option
  • Since it is difficult to turn it off, better displaying a deprecated warning, etc.

I would like to propose that we merge this change.