Restore previous interrupt handler after run

[deivid-rodriguez]

I was running puma's test suite, where rubocop is run before the test suite. One of the tests was hanging, and when pressing Ctrl-C to abort it, I would get rubocop's Ctrl-C handler run.

That seemed unexpected, I think rubocop should probably restore the previously installed handler after it's run?

---

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• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.
• Run rake default or rake parallel. It executes all tests and RuboCop for itself, and generates the documentation.

[bbatsov]

Seems like a good change to me, but it requires a changelog entry.

[rrosenblum]

The code looks good to me. Is it possible to write a test for this?

[deivid-rodriguez]

@bbatsov Changelog entry added!

The code looks good to me. Is it possible to write a test for this?

Of course it is, but I don't really feel very excited about it. If this is not good to go without a test I'll just leave this opened so anyone willing to do it (including future me) can pick it up! :)

[deivid-rodriguez]

Actually I'll add that test since this commit is actually breaking the default rubocop handler during rubocop test suite... Calling this WIP.

Not sure when I'll get to it though.

EDIT: Actually no, the behavior is the same as in master. During execution of spec/rubocop/cli_spec.rb, Ctrl-C doesn't seem to work. I'll add the test though.

[bbatsov]

OK, ping us when ready.

[bbatsov]

@deivid-rodriguez ping :-)

[deivid-rodriguez]

Hei @bbatsov, I don't think I'll get to this any time soon. I'll close this and reopen when I get time to complete it! :)

[deivid-rodriguez]

Ended up opening some separate PRs with a different approach to fix this, also with some testing!