Use static URL to download assets from latest release

[corneliusweig]

This also simplifies the release process for krew, because the version
number does not need to be updated when releasing a new version.

Fixes #...
Related issue: #...

[corneliusweig]

@ahmetb was there a particular reason why the version should be hardcoded and thus visible that I'm not aware of?

[codecov-io]

Codecov Report

Merging #513 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #513   +/-   ##
=======================================
  Coverage   59.12%   59.12%           
=======================================
  Files          23       23           
  Lines        1003     1003           
=======================================
  Hits          593      593           
  Misses        350      350           
  Partials       60       60

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[ahmetb]

I think we didn’t know “latest” worked?
That said I don’t understand removing the tagging instructions in Releasing.md.

[corneliusweig]

Oh it's because for a release we needed to adjust the hardcoded version number in README.md. That change needed to be committed, pushed, built, and fetched. All of these steps can now be skipped. The tagging step is still there I hope :).

[ahmetb]

Hmm but we still need this:

       git commit -m "Release ${TAG:?TAG required}"	

This ensures we have a clean commit that tags the release (we can add --allow-empty).

I frequently follow this pattern in my repos, it helps a lot in the GitHub web UI, as users go to a "commit" that explains the tag; not some irrelevant patch.

[corneliusweig]

Ok, that makes sense. Added back the instructions for creating a release commit.

[ahmetb]

/lgtm
/approve

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