support renamed default branches

[staabm]

the ref: input parameter seems to be hardcoded falling back to master.

https://github.com/actions/checkout/blob/master/README.md#L43-L46

since github support renaming the default branch, IMO the actions/checkout action should take this into account and therefore use the 'default-branch' as a fallback instead of always master

[ericsciple]

I wonder whether the default branch can be determined from the github event payload. Would enable implementing without making an extra call to the rest api.

[ericsciple]

It looks like the default branch can be retrieved from the event payload on disk:

      - run: |
          node -p "require(process.env.GITHUB_EVENT_PATH).repository.default_branch"

However that would only work for the workflow repo. For other repositories, would need to either query REST API or fallback to master

[mkalkbrenner]

An example is drupal/drupal which doesn't have a master branch at all which leads to this error:

  /usr/bin/git -c protocol.version=2 fetch --no-tags --prune --progress --no-recurse-submodules --depth=1 origin +refs/heads/master:refs/remotes/origin/master
  ##[error]fatal: couldn't find remote ref refs/heads/master
  The process '/usr/bin/git' failed with exit code 128

So from my point of view this is rather a bug than an enhancement ;-)

[ericsciple]

I played with the REST API a little bit. The default branch can be retrieved from the REST API.

I'm in favor of doing this feature, just havent gotten to it yet.

[brettwgreen]

A lot of people renaming their master branches lately... Haven't looked at this code, but maybe I'll take a look this weekend at making a PR unless you're close to picking this up.

[ericsciple]

looking into this now

[ericsciple]

PR #278 (testing now)