Add publish instructions.

.github/workflows/pythonpackage.yml

@@ -9,6 +9,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: [2.7, 3.6, 3.7, 3.8, pypy2, pypy3]
 
     steps:
     - uses: actions/checkout@v2
@@ -22,7 +23,7 @@ jobs:
         pip install -U pip coverage codecov flake8 fastimport
     - name: Style checks
       run: |
-        make style PYTHON=python
+        python -m flake8
     - name: Coverage test suite run
       run: |
         python -m coverage run -p -m unittest dulwich.tests.test_suite

.github/workflows/pythonpublish.yml

@@ -0,0 +1,32 @@
+name: Upload Python Package
+
+on:
+  release:
+    types: [created]
+
+jobs:
+  deploy:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ['2.x', '3.x']
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install setuptools wheel twine
+    - name: Build and publish
+      env:
+        TWINE_USERNAME: ${{ secrets.PYPI_USERNAME }}
+        TWINE_PASSWORD: ${{ secrets.PYPI_PASSWORD }}
+      run: |
+        python setup.py sdist bdist_wheel
+        twine upload dist/*