Use origin/master as baseline for schema version check

[corneliusweig]

Description

This is just a small teak to improve the usability of the schema version test.

Before it used the master branch as the reference version. However, this branch is not automatically updated by git when fetching changes from remote. On the other hand, the origin/master branch is reset to the newest version on every pull/fetch from origin. Hence, the reference version automatically updates even if the user never updates his master branch.

This assumes that users have a standard setup for remote repository names. But I think this is as widespread as the name master.

User facing changes

n/a

Next PRs.

n/a

Submitter Checklist

n/a

Reviewer Notes

• The code flow looks good.
• Unit test added.
• User facing changes look good.

[codecov]

Codecov Report

Merging #3501 into master will decrease coverage by 0.03%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
pkg/skaffold/util/tar.go	52.87% <0%> (-4.6%)	⬇️

[corneliusweig]

Hmm.. the failing kaniko test seems unrelated to me.

[dgageot]

yeah, let's ignore that