Fix a condition check on PyPI release workflow (#52)

Summary:
Pull Request resolved: #52

1. There was a small bug in the PyPI release workflow where I accidentally inverted the true/false condition on whether a new version should be released or not.
2. However, (1) means that the workflow should've been triggered. The only reason it wasn't is that, by default, the `checkout` action only pull the latest commit without any history... [so using `git tag` in workflow does not return anything](actions/checkout#100)
3. To fix (2), we should use `git ls-remote` to check the existing tags on GitHub (instead of listing the local ones). Cloning the repo with full history also works, but is much less efficient.

Reviewed By: nimar

Differential Revision: D24696408

fbshipit-source-id: f0834187672acf28eabd06466b519405f487fc52

.github/workflows/main.yml

@@ -118,10 +118,11 @@ jobs:
       id: version
       run: |
         VERSION_TAG="v$(python setup.py --version)"
-        if  [[ $(git tag -l $VERSION_TAG) ]]; then
-          echo "::set-output name=has_updated::true"
-        else
+        if  [[ $(git ls-remote --tags origin refs/tags/$VERSION_TAG) ]]; then
+          # there exists a tag with same name as current version
           echo "::set-output name=has_updated::false"
+        else
+          echo "::set-output name=has_updated::true"
         fi
         echo "::set-output name=version_tag::$(echo $VERSION_TAG)"
         echo "The current version of PPL Bench is $VERSION_TAG"