cmd/govim: add tests to verify turning off unimported completions works (#687)

[tjcain]

Following d80f0e2 unimported completions are turned on by default. This
commit adds tests to ensure setting CompleteUnimported to false disables
completion for unimported packages.

[myitcv]

@tjcain - thanks very much. Just a couple of questions/comments.

[myitcv]

LGTM. Will merge once build goes green.

Thank you, @tjcain!

[myitcv]

@tjcain - sorry, one thing I've just spotted (reviewing the commit message is not, sadly, part of GitHub's flow here, unlike Gerrit).

The (#xxx) suffix is added to commits automatically by GitHub because we are using "squash and merge". But despite using that feature per the wiki we rely on the commit message being "good", otherwise if left unsquashed the person doing the merge has to do the hard work of coming up with a good message!

Your message is great, with the exception of some really small nits:

• the superfluous suffix on the first line - this will simply be confusing when the PR is merged because it refers to the issue you are fixing. It will become the PR number itself so the linear history of govim can be quickly and easily traced back to the PRs that created commits
• the first line is a bit verbose
• the message is missing the "Fixes" directive

Therefore, how about something like?

cmd/govim: verify turning off unimported completions works

Following d80f0e2 unimported completions are turned on by default. This
commit adds tests to ensure setting CompleteUnimported to false disables
completion for unimported packages.

Fixes #687

That way #687 will be closed automatically when we merged.

Thanks

[tjcain]

@tjcain - sorry, one thing I've just spotted (reviewing the commit message is not, sadly, part of GitHub's flow here, unlike Gerrit).

I will get that fixed up now, thank you for the great feedback.

[myitcv]

Will ignore the macOS flake for now