Allow customization of master branch image name

[denisgranha]

For some projects it might be confusing to have latest being master branch instead of the latest tagged docker image.

In the case of https://github.com/openethereum/openethereum for example, we want to tag master as "nightly"

[elgohr]

Thank you for the PR at first.
It would have been great, if you would have discussed this in the issues first.
There's already a way to set custom tags for individual branches (https://github.com/elgohr/Publish-Docker-Github-Action/blob/master/README.md#tags-1).
In this way I don't see a need for this

[denisgranha]

hi @elgohr thanks for you fast reply!
But that’s not the same right? It will push also “latest” for master and we want to avoid that

[denisgranha]

ah, but this is actually missing something. I forgot to add the var to this line https://github.com/denisgranha/Publish-Docker-Github-Action/blob/master/entrypoint.sh#L96

[denisgranha]

but you say that by using custom tags, that has priority. Ok I can see in https://github.com/denisgranha/Publish-Docker-Github-Action/blob/master/entrypoint.sh#L92

will try then, thx

[elgohr]

name: Publish to Nightly
on:    
  push:
    branches:
      - master
jobs:
  update:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@master
    - name: Publish to Registry
      uses: elgohr/Publish-Docker-Github-Action@master
      with:
        name: myDocker/repository
        username: ${{ secrets.DOCKER_USERNAME }}
        password: ${{ secrets.DOCKER_PASSWORD }}
        tags: "nightly"

will push master to nightly.
See https://github.com/elgohr/Publish-Docker-Github-Action/blob/master/test.bats#L540