CI: switch to actions/checkout@v2

[XhmikosR]

Should speed things up a bit.

[mikemimik]

Small change to the ci.yml file. The change doesn't need to be reflected in benchmark.yml because we're not using the repo really.

Note to future selves (@npm/cli-team): might be worth removing that git checkout from the yaml.

[mikemimik]

The fetch depth defaults to 1 with the new version of actions/checkout. Ordinarily I don't think this would matter, but we've seen some weirdness with depth: 1 checkouts, and I'd rather avoid this for now. We can always adjust this later in the future.

Suggested change

	- uses: actions/checkout@v2
	- uses: actions/checkout@v2
	with:
	fetch-depth: 0

[mikemimik]

From the docs on actions/checkout

# Number of commits to fetch. 0 indicates all history.
# Default: 1
fetch-depth: ''

[XhmikosR]

I don't agree you need this, unless it causes problems, which it shouldn't.

[XhmikosR]

To elaborate more, the whole point of this patch is to make use of the new defaults which includes depth 1, which in turn speeds things up. So, unless this causes a problem, there's no reason to proactively change the defaults.

[mikemimik]

We'll validate the changes don't break things on our release branch, and if they don't we'll pull the changes in :)