docs(github): fixes env var flag details (#244)

Details:

* The docs section 'Github Actions Gotcha' stated that the COVERALLS_FLAG_NAME
  env var is needed in order to avoid 'pile up of jobs'. It turns out that
  it is optional, and when specified, can be specified with the same value
  across all jobs or with unique values.
  This change clarifies that in the documentation.

* This change also clarifies that the COVERALLS_REPO_TOKEN env var is not needed
  for GitHub Actions.

* This change also renames the heading of the section to 'Github Actions support'
  to have a more neutral name.

Signed-off-by: Andreas Maier <andreas.r.maier@gmx.de>

docs/usage/configuration.rst

@@ -21,7 +21,7 @@ If you would like to override the service name (auto-discovered on most CI syste
 
 If you are interested in merging the coverage results between multiple languages/projects, see our :ref:`multi-language <multilang>` documentation.
 
-If coveralls-python is being run on TravisCI, it will automatically set the token for communication with coveralls.io. Otherwise, you should set the environment variable ``COVERALLS_REPO_TOKEN``, which can be found on the dashboard for your project in coveralls.io::
+If coveralls-python is being run on TravisCI or on GitHub Actions, it will automatically set the token for communication with coveralls.io. Otherwise, you should set the environment variable ``COVERALLS_REPO_TOKEN``, which can be found on the dashboard for your project in coveralls.io::
 
     COVERALLS_REPO_TOKEN=mV2Jajb8y3c6AFlcVNagHO20fiZNkXPVy coveralls
 
@@ -54,8 +54,8 @@ Sample ``.coveralls.yml`` file::
     parallel: true
     coveralls_host: https://coveralls.aperture.com
 
-Github Actions Gotcha
----------------------
+Github Actions support
+----------------------
 
 Coveralls natively supports jobs running on Github Actions. You can directly pass the default-provided secret GITHUB_TOKEN::
 
@@ -64,7 +64,12 @@ Coveralls natively supports jobs running on Github Actions. You can directly pas
     run: |
         coveralls
 
-For parallel builds, you have to add a final step to let coveralls know the parallel build is finished. You also have to set COVERALLS_FLAG_NAME to something unique to the specific step, so re-runs of the same job don't keep piling up builds::
+Passing a coveralls.io token via the ``COVERALLS_REPO_TOKEN`` environment variable
+(or via the ``repo_token`` parameter in the config file) is not needed for
+Github Actions.
+
+For parallel builds, you have to add a final step to let coveralls.io know the
+parallel build is finished::
 
     jobs:
       test:
@@ -79,14 +84,14 @@ For parallel builds, you have to add a final step to let coveralls know the para
             uses: actions/checkout@v2
           - name: Test
             run: ./run_tests.sh ${{ matrix.test-name }}
-          - name: Upload Coverage
+          - name: Upload coverage data to coveralls.io
             run: coveralls
             env:
               GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
               COVERALLS_FLAG_NAME: ${{ matrix.test-name }}
               COVERALLS_PARALLEL: true
       coveralls:
-        name: Finish Coveralls
+        name: Indicate completion to coveralls.io
         needs: test
         runs-on: ubuntu-latest
         container: python:3-slim
@@ -97,3 +102,7 @@ For parallel builds, you have to add a final step to let coveralls know the para
             coveralls --finish
           env:
             GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+The ``COVERALLS_FLAG_NAME`` environment variable (or the ``flag_name`` parameter
+in the config file) is optional and can be used to better identify each job
+on coveralls.io. It does not need to be unique across the parallel jobs.