Migrate CI from Travis to GitHub Actions

Replace the Travis config with a tests workflow on GitHub Actions:
style job (black, flake8, pep8-naming) and a Python 3.9-3.12 test
matrix, with coverage uploaded via codecov-action@v4. README badges
updated to point at the new workflow and the main branch.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: tgamblin

.github/workflows/tests.yml

@@ -0,0 +1,51 @@
+name: tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  style:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - name: Install style tools
+        run: |
+          python -m pip install --upgrade pip
+          pip install black flake8 pep8-naming
+      - name: black
+        run: black --diff --check .
+      - name: flake8
+        run: flake8
+
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ['3.9', '3.10', '3.11', '3.12']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt coverage
+          pip install -e .
+      - name: Run tests
+        run: PYTHONPATH=. coverage run $(which pytest)
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          flags: py${{ matrix.python-version }}
+          token: ${{ secrets.CODECOV_TOKEN }}
+        env:
+          OS: ${{ runner.os }}
+          PYTHON: ${{ matrix.python-version }}

.travis.yml

@@ -1,8 +1,8 @@
 # Contrib
 
 [![PyPI version](https://badge.fury.io/py/contrib.svg)](https://badge.fury.io/py/contrib)
-[![Build Status](https://travis-ci.com/spack/contrib.svg?branch=master)](https://travis-ci.com/spack/contrib)
-[![codecov](https://codecov.io/gh/spack/contrib/branch/master/graph/badge.svg)](https://codecov.io/gh/spack/contrib)
+[![tests](https://github.com/spack/contrib/actions/workflows/tests.yml/badge.svg?branch=main)](https://github.com/spack/contrib/actions/workflows/tests.yml)
+[![codecov](https://codecov.io/gh/spack/contrib/branch/main/graph/badge.svg)](https://codecov.io/gh/spack/contrib)
 [![Code Style: Black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
 A python package for making stacked area plots of contributions to a git