Document path restrictions

[narqo]

After some experiments, it seems that path argument has restrictions on what values can be used. That is, I have tried making checkout to clone the repo into GOPATH workspace, e.g. I required the clone path to be exactly $GOPATH/src/github.com/<owner>/<repo>, but none of the following worked as expected:

Both following variants fired an error that looked like the value of the path couldn't be absolute:

- uses: actions/checkout@v1
  with:
    path: /home/runner/go/src/github.com/${{ github.repository }}

- uses: actions/checkout@v1
  with:
    path: ${{ runner.workspace }}/src/github.com/${{ github.repository }}

The following produced the same error, even though the path wasn't an absolute:

- uses: actions/checkout@v1
  with:
    path: src/github.com/${{ github.repository }}

The following worked, but checkout didn't expand the value of $GOPATH:

- uses: actions/checkout@v1
  with:
    path: $GOPATH/src/github.com/${{ github.repository }}
  env:
    GOPATH: ${{ runner.workspace }}

The only way to made it work as I needed was the following

- uses: actions/checkout@v1
  with:
    path: ./src/github.com/${{ github.repository }}

With the above configuration, I could use env: GOPATH: ${{ runner.workspace }} in the subsequent run steps. See the full example in the PR profefe/profefe#34

That's being said, the restrictions for path requires some clarification.

[ncw]

Thanks for working this out - very helpful :-)

[elgohr]

Some more documentation would be really useful.
Here is another interpretation of path
elgohr/Publish-Docker-Github-Action#23

[ericsciple]

i updated the docs in master which is now v2-beta. I'll push a v2 tag tomorrow