Added GitHub Actions CI detection.

[nmoinvaz]

I initially had to do this before GitHub Actions was public. I now updated/copied from the bash uploader.

[codecov]

Codecov Report

Merging #265 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #265   +/-   ##
=====================================
  Coverage      88%    88%           
=====================================
  Files           2      2           
  Lines           9      9           
=====================================
  Hits            8      8           
  Misses          1      1           

[hoefling]

@nmoinvaz shouldn't this obsolete the necessity of passing the token explicitly? When trying the tokenless upload, I still get the message Error: Missing repository upload token (example job, install codecov from this PR). No issue when using the bash uploader, though (example job using bash uploader).

[nmoinvaz]

I'm not sure how tokenless works. This PR only gets the environment variable values when running on GitHub Actions environment and uses them in the upload to Codecov.

[alecgerona]

Any updates on this? This is especially useful for running tests inside tox since it has issues running the bash uploader. It can't detect if it's running from Github Actions.

[thomasrockhu]

Thanks @nmoinvaz on this, could we get some tests for this new behavior?

[nmoinvaz]

Done.

[thomasrockhu]

LGTM